Lecture Notes for Math 1000 Xiang-Sheng Wang Memorial University of Newfoundland Office: HH-2016, Phone: 864-4321 Office hour: 10:00-11:30 Monday, Tuesday and Wednesday Email: [email protected]or [email protected]Course website: http://www.ucs.mun.ca/ ~ xiangshengw/math1000.html Lecture Notes for Math 1000 First Previous Next Last 1
89
Embed
Lecture Notes for Math 1000 - Memorial University of ...xiangshengw/math1000/math1000.pdf · Explained the material clearly. ... Xiangsheng Wang methods are much better from going
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Lecture Notes for Math 1000
Xiang-Sheng Wang
Memorial University of Newfoundland
Office HH-2016 Phone 864-4321
Office hour 1000-1130 Monday Tuesday and Wednesday
Lecture Notes for Math 1000 First Previous Next Last 1
Self-introduction
bull Name Xiang-Sheng Wang
bull Position Teaching postdoctoral fellow
bull PhD received 2009
bull Previous affiliation York University
bull Teaching experience
1 Math 1013 (Applied Calculus I)2 Math 1190 (Introduction to Sets and Logic)3 Math 1540 (Introductory Mathematics for Economists II)4 Math 6378 (Applied Delay Differential Equations graduate course)
Lecture Notes for Math 1000 First Previous Next Last 2
What did my previous students say about me
bull Professor presented the material in a way that made it feel was less overwellingExplained the material clearly I thought the professor made a great effort tohave students understand what was being taught in lecture
bull The thing the made me want to come to class is number of examples beingused to demonstrate a theorem and not just doing an easy example and thatbeing the end of it Xiangsheng Wang methods are much better from going toa easy question to a tougher question so we know what we can expect in thehomework Also there is no real rush everything is done properly and everyminute is used well
bull I valued the professorrsquos teaching style He was able to convey concepts andrules very clearly so a student would be able to follow step-by-step in thecalculations and problem solutions
Lecture Notes for Math 1000 First Previous Next Last 3
What did my previous students say about me
bull Teacher showed me that math is not impossible
bull The Professor took EXTRA SPECIAL interest in teaching us He didnt justrandomly scroll through presentation slides He put up MANY examplessumson the chalk board which we could write down in our notebooks amp revise laterNO OTHER PROFESSOR has done that till date Especially in a subject likeMath this is of prime importance He made sure each one of us understoodwhat he was teaching
bull Professor Wang is able to deliever the course material effectively and efficientlyHe provides many examples to ensure we understand the material Amazingprof
Lecture Notes for Math 1000 First Previous Next Last 4
What did my previous students say about me
bull I found it easier to understand everything from Professor Xiangsheng Wang andI think overall everyone is doing better in this class Also the instructor goesout his way to answer questions through email which is very convenient whenyou can not make the office hours
bull The Professor loves doing what he does best - teaching He would allot time tous students even outside his office hours to explain us the material
bull The Professor set exam papers which checked our knowledge about thematerial not unnecessarily tough questions to pressure us
bull The Professor not only wrote many examples on the board along withdefinitions etc but also presented slides and explained the concepts therein indetail once again which were concise amp useful for later reference
Lecture Notes for Math 1000 First Previous Next Last 5
What can you benefit from me
bull I will show you that mathematics is not impossible I will try my best efforts tohelp you understand the materials in this course by using many illustrativeexamples
bull I am always willing to answer your questions So please do not hesitate tocome to me whenever you have any
bull My contact information
Office HH-2016Office hour MTW 1000-1130 (or by appointment)Phone 864-4321Email xswang4gmailcom
Lecture Notes for Math 1000 First Previous Next Last 6
Outline
bull Textbook (either of the following two)
1 Calculus Early Transcendentals with WebAssign Access Card (bundle) byJon Rogawski OR
2 Math 1000 1001 Course Notes by Bruce Watson +Calculus Early Transcendentals WebAssign Card by Jon Rogawski
bull Topics to be covered limits and continuity differentiation and applications ofdifferentiation
bull Prerequisite Math 1090 or a combination of placement test and high schoolMathematics scores acceptable to the department
bull Marks 55 Final Exam 30 In-class tests (three tests with 10 each) 75WebAssign 75 Assignments
Lecture Notes for Math 1000 First Previous Next Last 7
Mathematics Placement Test
bull Students who are planning to do Math 1000 for the first time must write theMathematics Placement Test
bull The test will be administered for the last time this semester on Sep 11(Tuesday) at 1900 in HH-3017
bull Failure to write the MPT will result in deregistration from the course
bull The mark required to qualify for Math 1000 is 85 with Academic math 3204 or75 with Advanced math 3205
bull A synopsis of the MPT is available on the shelf (adjacent to HH-3009) acrossthe corridor from the General Office or online athttpwwwmuncamathmptsynopsis
Lecture Notes for Math 1000 First Previous Next Last 8
Assignments
bull Homework assignment must be handed in no later than 1400 on the due dateThey may be submitted in class or placed in the marking box Late assignmentwill NOT be marked
bull Assignments should be submitted on loose leaf 85rdquotimes 11rdquo paper stapled inthe upper left corner written on one side only with problems done in orderThey should not be placed in folders or any other container Assignmentsshould include a cover page with your name and student number the name ofthe course and the assignment number
bull If you are unable to submit an assignment due to illness bereavement or otheracceptable reason please provide me with appropriate documentation (egdoctorrsquos note death notice) and I will average together your remainingassignments to create a mark out of 75
Lecture Notes for Math 1000 First Previous Next Last 9
WebAssign
bull Website httpwwwmathmuncawebassign
bull The above website contains complete instructions for signing up for WebAssignand you should read it fully
bull In order to fully activate your WebAssign account you will need to purchase aWebAssign access code from the University Bookstore by September 18th
bull You MUST use your MUN email address when signing up for WebAssign
bull Should you have further questions with WebAssign please contact theWebAssign administrator Dr Sullivan (shannonmunca)
Lecture Notes for Math 1000 First Previous Next Last 10
Tests and exam
bull No notes textbooks calculators or any electronic communications device arepermitted during any test or final examination
bull There will be no make-up for a missed in-class test Upon presentation ofdocumentation of a valid excuse the corresponding percentage of the finalmark will be added to the final exam With no presentation of suchdocumentation a grade of zero will be entered for the missed test
bull Tentative dates for three in-class tests (will be confirmed in class)
1 Sep 28 Friday2 Oct 19 Friday3 Nov 09 Friday
Lecture Notes for Math 1000 First Previous Next Last 11
Supplementary exams
The Department of Mathematics and Statistics offers supplementary examinationsto students satisfying all of the following
bull the student is in clear academic standing
bull the student has a passing term mark and
bull the studentrsquos final grade is 45 to 49
Lecture Notes for Math 1000 First Previous Next Last 12
Whenever you need help
bull Math Help Center (HH-3015) stating from Sep 10 (Monday)
1000-1600 Monday Tuesday Wednesday and Thursday0900-1300 Friday
bull Office hour (HH-2016) 1000-1130 Monday Tuesday and Wednesday
bull Email xswang4gmailcom
bull Office phone number 864-4321
bull I am always willing to help you -)
Lecture Notes for Math 1000 First Previous Next Last 13
Niagara Falls ON
Lecture Notes for Math 1000 First Previous Next Last 14
St John River NB
Lecture Notes for Math 1000 First Previous Next Last 15
Difference between the falls and the river
bull The river has no jump It is continuous
bull The falls has a jump It is discontinuous
bull Question how to distinguish between continuity and discontinuity
bull Answer with the aid of limits
bull Remark Limits help us define continuity
Lecture Notes for Math 1000 First Previous Next Last 16
Continuity and discontinuity
The slides are continuous The stairs are discontinuous
Lecture Notes for Math 1000 First Previous Next Last 17
Discontinuity the unfinished bridge
The function is not defined at the discontinuous point
Lecture Notes for Math 1000 First Previous Next Last 18
Discontinuity the broken bridge
The limits from both sides do not match
Lecture Notes for Math 1000 First Previous Next Last 19
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Self-introduction
bull Name Xiang-Sheng Wang
bull Position Teaching postdoctoral fellow
bull PhD received 2009
bull Previous affiliation York University
bull Teaching experience
1 Math 1013 (Applied Calculus I)2 Math 1190 (Introduction to Sets and Logic)3 Math 1540 (Introductory Mathematics for Economists II)4 Math 6378 (Applied Delay Differential Equations graduate course)
Lecture Notes for Math 1000 First Previous Next Last 2
What did my previous students say about me
bull Professor presented the material in a way that made it feel was less overwellingExplained the material clearly I thought the professor made a great effort tohave students understand what was being taught in lecture
bull The thing the made me want to come to class is number of examples beingused to demonstrate a theorem and not just doing an easy example and thatbeing the end of it Xiangsheng Wang methods are much better from going toa easy question to a tougher question so we know what we can expect in thehomework Also there is no real rush everything is done properly and everyminute is used well
bull I valued the professorrsquos teaching style He was able to convey concepts andrules very clearly so a student would be able to follow step-by-step in thecalculations and problem solutions
Lecture Notes for Math 1000 First Previous Next Last 3
What did my previous students say about me
bull Teacher showed me that math is not impossible
bull The Professor took EXTRA SPECIAL interest in teaching us He didnt justrandomly scroll through presentation slides He put up MANY examplessumson the chalk board which we could write down in our notebooks amp revise laterNO OTHER PROFESSOR has done that till date Especially in a subject likeMath this is of prime importance He made sure each one of us understoodwhat he was teaching
bull Professor Wang is able to deliever the course material effectively and efficientlyHe provides many examples to ensure we understand the material Amazingprof
Lecture Notes for Math 1000 First Previous Next Last 4
What did my previous students say about me
bull I found it easier to understand everything from Professor Xiangsheng Wang andI think overall everyone is doing better in this class Also the instructor goesout his way to answer questions through email which is very convenient whenyou can not make the office hours
bull The Professor loves doing what he does best - teaching He would allot time tous students even outside his office hours to explain us the material
bull The Professor set exam papers which checked our knowledge about thematerial not unnecessarily tough questions to pressure us
bull The Professor not only wrote many examples on the board along withdefinitions etc but also presented slides and explained the concepts therein indetail once again which were concise amp useful for later reference
Lecture Notes for Math 1000 First Previous Next Last 5
What can you benefit from me
bull I will show you that mathematics is not impossible I will try my best efforts tohelp you understand the materials in this course by using many illustrativeexamples
bull I am always willing to answer your questions So please do not hesitate tocome to me whenever you have any
bull My contact information
Office HH-2016Office hour MTW 1000-1130 (or by appointment)Phone 864-4321Email xswang4gmailcom
Lecture Notes for Math 1000 First Previous Next Last 6
Outline
bull Textbook (either of the following two)
1 Calculus Early Transcendentals with WebAssign Access Card (bundle) byJon Rogawski OR
2 Math 1000 1001 Course Notes by Bruce Watson +Calculus Early Transcendentals WebAssign Card by Jon Rogawski
bull Topics to be covered limits and continuity differentiation and applications ofdifferentiation
bull Prerequisite Math 1090 or a combination of placement test and high schoolMathematics scores acceptable to the department
bull Marks 55 Final Exam 30 In-class tests (three tests with 10 each) 75WebAssign 75 Assignments
Lecture Notes for Math 1000 First Previous Next Last 7
Mathematics Placement Test
bull Students who are planning to do Math 1000 for the first time must write theMathematics Placement Test
bull The test will be administered for the last time this semester on Sep 11(Tuesday) at 1900 in HH-3017
bull Failure to write the MPT will result in deregistration from the course
bull The mark required to qualify for Math 1000 is 85 with Academic math 3204 or75 with Advanced math 3205
bull A synopsis of the MPT is available on the shelf (adjacent to HH-3009) acrossthe corridor from the General Office or online athttpwwwmuncamathmptsynopsis
Lecture Notes for Math 1000 First Previous Next Last 8
Assignments
bull Homework assignment must be handed in no later than 1400 on the due dateThey may be submitted in class or placed in the marking box Late assignmentwill NOT be marked
bull Assignments should be submitted on loose leaf 85rdquotimes 11rdquo paper stapled inthe upper left corner written on one side only with problems done in orderThey should not be placed in folders or any other container Assignmentsshould include a cover page with your name and student number the name ofthe course and the assignment number
bull If you are unable to submit an assignment due to illness bereavement or otheracceptable reason please provide me with appropriate documentation (egdoctorrsquos note death notice) and I will average together your remainingassignments to create a mark out of 75
Lecture Notes for Math 1000 First Previous Next Last 9
WebAssign
bull Website httpwwwmathmuncawebassign
bull The above website contains complete instructions for signing up for WebAssignand you should read it fully
bull In order to fully activate your WebAssign account you will need to purchase aWebAssign access code from the University Bookstore by September 18th
bull You MUST use your MUN email address when signing up for WebAssign
bull Should you have further questions with WebAssign please contact theWebAssign administrator Dr Sullivan (shannonmunca)
Lecture Notes for Math 1000 First Previous Next Last 10
Tests and exam
bull No notes textbooks calculators or any electronic communications device arepermitted during any test or final examination
bull There will be no make-up for a missed in-class test Upon presentation ofdocumentation of a valid excuse the corresponding percentage of the finalmark will be added to the final exam With no presentation of suchdocumentation a grade of zero will be entered for the missed test
bull Tentative dates for three in-class tests (will be confirmed in class)
1 Sep 28 Friday2 Oct 19 Friday3 Nov 09 Friday
Lecture Notes for Math 1000 First Previous Next Last 11
Supplementary exams
The Department of Mathematics and Statistics offers supplementary examinationsto students satisfying all of the following
bull the student is in clear academic standing
bull the student has a passing term mark and
bull the studentrsquos final grade is 45 to 49
Lecture Notes for Math 1000 First Previous Next Last 12
Whenever you need help
bull Math Help Center (HH-3015) stating from Sep 10 (Monday)
1000-1600 Monday Tuesday Wednesday and Thursday0900-1300 Friday
bull Office hour (HH-2016) 1000-1130 Monday Tuesday and Wednesday
bull Email xswang4gmailcom
bull Office phone number 864-4321
bull I am always willing to help you -)
Lecture Notes for Math 1000 First Previous Next Last 13
Niagara Falls ON
Lecture Notes for Math 1000 First Previous Next Last 14
St John River NB
Lecture Notes for Math 1000 First Previous Next Last 15
Difference between the falls and the river
bull The river has no jump It is continuous
bull The falls has a jump It is discontinuous
bull Question how to distinguish between continuity and discontinuity
bull Answer with the aid of limits
bull Remark Limits help us define continuity
Lecture Notes for Math 1000 First Previous Next Last 16
Continuity and discontinuity
The slides are continuous The stairs are discontinuous
Lecture Notes for Math 1000 First Previous Next Last 17
Discontinuity the unfinished bridge
The function is not defined at the discontinuous point
Lecture Notes for Math 1000 First Previous Next Last 18
Discontinuity the broken bridge
The limits from both sides do not match
Lecture Notes for Math 1000 First Previous Next Last 19
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
What did my previous students say about me
bull Professor presented the material in a way that made it feel was less overwellingExplained the material clearly I thought the professor made a great effort tohave students understand what was being taught in lecture
bull The thing the made me want to come to class is number of examples beingused to demonstrate a theorem and not just doing an easy example and thatbeing the end of it Xiangsheng Wang methods are much better from going toa easy question to a tougher question so we know what we can expect in thehomework Also there is no real rush everything is done properly and everyminute is used well
bull I valued the professorrsquos teaching style He was able to convey concepts andrules very clearly so a student would be able to follow step-by-step in thecalculations and problem solutions
Lecture Notes for Math 1000 First Previous Next Last 3
What did my previous students say about me
bull Teacher showed me that math is not impossible
bull The Professor took EXTRA SPECIAL interest in teaching us He didnt justrandomly scroll through presentation slides He put up MANY examplessumson the chalk board which we could write down in our notebooks amp revise laterNO OTHER PROFESSOR has done that till date Especially in a subject likeMath this is of prime importance He made sure each one of us understoodwhat he was teaching
bull Professor Wang is able to deliever the course material effectively and efficientlyHe provides many examples to ensure we understand the material Amazingprof
Lecture Notes for Math 1000 First Previous Next Last 4
What did my previous students say about me
bull I found it easier to understand everything from Professor Xiangsheng Wang andI think overall everyone is doing better in this class Also the instructor goesout his way to answer questions through email which is very convenient whenyou can not make the office hours
bull The Professor loves doing what he does best - teaching He would allot time tous students even outside his office hours to explain us the material
bull The Professor set exam papers which checked our knowledge about thematerial not unnecessarily tough questions to pressure us
bull The Professor not only wrote many examples on the board along withdefinitions etc but also presented slides and explained the concepts therein indetail once again which were concise amp useful for later reference
Lecture Notes for Math 1000 First Previous Next Last 5
What can you benefit from me
bull I will show you that mathematics is not impossible I will try my best efforts tohelp you understand the materials in this course by using many illustrativeexamples
bull I am always willing to answer your questions So please do not hesitate tocome to me whenever you have any
bull My contact information
Office HH-2016Office hour MTW 1000-1130 (or by appointment)Phone 864-4321Email xswang4gmailcom
Lecture Notes for Math 1000 First Previous Next Last 6
Outline
bull Textbook (either of the following two)
1 Calculus Early Transcendentals with WebAssign Access Card (bundle) byJon Rogawski OR
2 Math 1000 1001 Course Notes by Bruce Watson +Calculus Early Transcendentals WebAssign Card by Jon Rogawski
bull Topics to be covered limits and continuity differentiation and applications ofdifferentiation
bull Prerequisite Math 1090 or a combination of placement test and high schoolMathematics scores acceptable to the department
bull Marks 55 Final Exam 30 In-class tests (three tests with 10 each) 75WebAssign 75 Assignments
Lecture Notes for Math 1000 First Previous Next Last 7
Mathematics Placement Test
bull Students who are planning to do Math 1000 for the first time must write theMathematics Placement Test
bull The test will be administered for the last time this semester on Sep 11(Tuesday) at 1900 in HH-3017
bull Failure to write the MPT will result in deregistration from the course
bull The mark required to qualify for Math 1000 is 85 with Academic math 3204 or75 with Advanced math 3205
bull A synopsis of the MPT is available on the shelf (adjacent to HH-3009) acrossthe corridor from the General Office or online athttpwwwmuncamathmptsynopsis
Lecture Notes for Math 1000 First Previous Next Last 8
Assignments
bull Homework assignment must be handed in no later than 1400 on the due dateThey may be submitted in class or placed in the marking box Late assignmentwill NOT be marked
bull Assignments should be submitted on loose leaf 85rdquotimes 11rdquo paper stapled inthe upper left corner written on one side only with problems done in orderThey should not be placed in folders or any other container Assignmentsshould include a cover page with your name and student number the name ofthe course and the assignment number
bull If you are unable to submit an assignment due to illness bereavement or otheracceptable reason please provide me with appropriate documentation (egdoctorrsquos note death notice) and I will average together your remainingassignments to create a mark out of 75
Lecture Notes for Math 1000 First Previous Next Last 9
WebAssign
bull Website httpwwwmathmuncawebassign
bull The above website contains complete instructions for signing up for WebAssignand you should read it fully
bull In order to fully activate your WebAssign account you will need to purchase aWebAssign access code from the University Bookstore by September 18th
bull You MUST use your MUN email address when signing up for WebAssign
bull Should you have further questions with WebAssign please contact theWebAssign administrator Dr Sullivan (shannonmunca)
Lecture Notes for Math 1000 First Previous Next Last 10
Tests and exam
bull No notes textbooks calculators or any electronic communications device arepermitted during any test or final examination
bull There will be no make-up for a missed in-class test Upon presentation ofdocumentation of a valid excuse the corresponding percentage of the finalmark will be added to the final exam With no presentation of suchdocumentation a grade of zero will be entered for the missed test
bull Tentative dates for three in-class tests (will be confirmed in class)
1 Sep 28 Friday2 Oct 19 Friday3 Nov 09 Friday
Lecture Notes for Math 1000 First Previous Next Last 11
Supplementary exams
The Department of Mathematics and Statistics offers supplementary examinationsto students satisfying all of the following
bull the student is in clear academic standing
bull the student has a passing term mark and
bull the studentrsquos final grade is 45 to 49
Lecture Notes for Math 1000 First Previous Next Last 12
Whenever you need help
bull Math Help Center (HH-3015) stating from Sep 10 (Monday)
1000-1600 Monday Tuesday Wednesday and Thursday0900-1300 Friday
bull Office hour (HH-2016) 1000-1130 Monday Tuesday and Wednesday
bull Email xswang4gmailcom
bull Office phone number 864-4321
bull I am always willing to help you -)
Lecture Notes for Math 1000 First Previous Next Last 13
Niagara Falls ON
Lecture Notes for Math 1000 First Previous Next Last 14
St John River NB
Lecture Notes for Math 1000 First Previous Next Last 15
Difference between the falls and the river
bull The river has no jump It is continuous
bull The falls has a jump It is discontinuous
bull Question how to distinguish between continuity and discontinuity
bull Answer with the aid of limits
bull Remark Limits help us define continuity
Lecture Notes for Math 1000 First Previous Next Last 16
Continuity and discontinuity
The slides are continuous The stairs are discontinuous
Lecture Notes for Math 1000 First Previous Next Last 17
Discontinuity the unfinished bridge
The function is not defined at the discontinuous point
Lecture Notes for Math 1000 First Previous Next Last 18
Discontinuity the broken bridge
The limits from both sides do not match
Lecture Notes for Math 1000 First Previous Next Last 19
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
What did my previous students say about me
bull Teacher showed me that math is not impossible
bull The Professor took EXTRA SPECIAL interest in teaching us He didnt justrandomly scroll through presentation slides He put up MANY examplessumson the chalk board which we could write down in our notebooks amp revise laterNO OTHER PROFESSOR has done that till date Especially in a subject likeMath this is of prime importance He made sure each one of us understoodwhat he was teaching
bull Professor Wang is able to deliever the course material effectively and efficientlyHe provides many examples to ensure we understand the material Amazingprof
Lecture Notes for Math 1000 First Previous Next Last 4
What did my previous students say about me
bull I found it easier to understand everything from Professor Xiangsheng Wang andI think overall everyone is doing better in this class Also the instructor goesout his way to answer questions through email which is very convenient whenyou can not make the office hours
bull The Professor loves doing what he does best - teaching He would allot time tous students even outside his office hours to explain us the material
bull The Professor set exam papers which checked our knowledge about thematerial not unnecessarily tough questions to pressure us
bull The Professor not only wrote many examples on the board along withdefinitions etc but also presented slides and explained the concepts therein indetail once again which were concise amp useful for later reference
Lecture Notes for Math 1000 First Previous Next Last 5
What can you benefit from me
bull I will show you that mathematics is not impossible I will try my best efforts tohelp you understand the materials in this course by using many illustrativeexamples
bull I am always willing to answer your questions So please do not hesitate tocome to me whenever you have any
bull My contact information
Office HH-2016Office hour MTW 1000-1130 (or by appointment)Phone 864-4321Email xswang4gmailcom
Lecture Notes for Math 1000 First Previous Next Last 6
Outline
bull Textbook (either of the following two)
1 Calculus Early Transcendentals with WebAssign Access Card (bundle) byJon Rogawski OR
2 Math 1000 1001 Course Notes by Bruce Watson +Calculus Early Transcendentals WebAssign Card by Jon Rogawski
bull Topics to be covered limits and continuity differentiation and applications ofdifferentiation
bull Prerequisite Math 1090 or a combination of placement test and high schoolMathematics scores acceptable to the department
bull Marks 55 Final Exam 30 In-class tests (three tests with 10 each) 75WebAssign 75 Assignments
Lecture Notes for Math 1000 First Previous Next Last 7
Mathematics Placement Test
bull Students who are planning to do Math 1000 for the first time must write theMathematics Placement Test
bull The test will be administered for the last time this semester on Sep 11(Tuesday) at 1900 in HH-3017
bull Failure to write the MPT will result in deregistration from the course
bull The mark required to qualify for Math 1000 is 85 with Academic math 3204 or75 with Advanced math 3205
bull A synopsis of the MPT is available on the shelf (adjacent to HH-3009) acrossthe corridor from the General Office or online athttpwwwmuncamathmptsynopsis
Lecture Notes for Math 1000 First Previous Next Last 8
Assignments
bull Homework assignment must be handed in no later than 1400 on the due dateThey may be submitted in class or placed in the marking box Late assignmentwill NOT be marked
bull Assignments should be submitted on loose leaf 85rdquotimes 11rdquo paper stapled inthe upper left corner written on one side only with problems done in orderThey should not be placed in folders or any other container Assignmentsshould include a cover page with your name and student number the name ofthe course and the assignment number
bull If you are unable to submit an assignment due to illness bereavement or otheracceptable reason please provide me with appropriate documentation (egdoctorrsquos note death notice) and I will average together your remainingassignments to create a mark out of 75
Lecture Notes for Math 1000 First Previous Next Last 9
WebAssign
bull Website httpwwwmathmuncawebassign
bull The above website contains complete instructions for signing up for WebAssignand you should read it fully
bull In order to fully activate your WebAssign account you will need to purchase aWebAssign access code from the University Bookstore by September 18th
bull You MUST use your MUN email address when signing up for WebAssign
bull Should you have further questions with WebAssign please contact theWebAssign administrator Dr Sullivan (shannonmunca)
Lecture Notes for Math 1000 First Previous Next Last 10
Tests and exam
bull No notes textbooks calculators or any electronic communications device arepermitted during any test or final examination
bull There will be no make-up for a missed in-class test Upon presentation ofdocumentation of a valid excuse the corresponding percentage of the finalmark will be added to the final exam With no presentation of suchdocumentation a grade of zero will be entered for the missed test
bull Tentative dates for three in-class tests (will be confirmed in class)
1 Sep 28 Friday2 Oct 19 Friday3 Nov 09 Friday
Lecture Notes for Math 1000 First Previous Next Last 11
Supplementary exams
The Department of Mathematics and Statistics offers supplementary examinationsto students satisfying all of the following
bull the student is in clear academic standing
bull the student has a passing term mark and
bull the studentrsquos final grade is 45 to 49
Lecture Notes for Math 1000 First Previous Next Last 12
Whenever you need help
bull Math Help Center (HH-3015) stating from Sep 10 (Monday)
1000-1600 Monday Tuesday Wednesday and Thursday0900-1300 Friday
bull Office hour (HH-2016) 1000-1130 Monday Tuesday and Wednesday
bull Email xswang4gmailcom
bull Office phone number 864-4321
bull I am always willing to help you -)
Lecture Notes for Math 1000 First Previous Next Last 13
Niagara Falls ON
Lecture Notes for Math 1000 First Previous Next Last 14
St John River NB
Lecture Notes for Math 1000 First Previous Next Last 15
Difference between the falls and the river
bull The river has no jump It is continuous
bull The falls has a jump It is discontinuous
bull Question how to distinguish between continuity and discontinuity
bull Answer with the aid of limits
bull Remark Limits help us define continuity
Lecture Notes for Math 1000 First Previous Next Last 16
Continuity and discontinuity
The slides are continuous The stairs are discontinuous
Lecture Notes for Math 1000 First Previous Next Last 17
Discontinuity the unfinished bridge
The function is not defined at the discontinuous point
Lecture Notes for Math 1000 First Previous Next Last 18
Discontinuity the broken bridge
The limits from both sides do not match
Lecture Notes for Math 1000 First Previous Next Last 19
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
What did my previous students say about me
bull I found it easier to understand everything from Professor Xiangsheng Wang andI think overall everyone is doing better in this class Also the instructor goesout his way to answer questions through email which is very convenient whenyou can not make the office hours
bull The Professor loves doing what he does best - teaching He would allot time tous students even outside his office hours to explain us the material
bull The Professor set exam papers which checked our knowledge about thematerial not unnecessarily tough questions to pressure us
bull The Professor not only wrote many examples on the board along withdefinitions etc but also presented slides and explained the concepts therein indetail once again which were concise amp useful for later reference
Lecture Notes for Math 1000 First Previous Next Last 5
What can you benefit from me
bull I will show you that mathematics is not impossible I will try my best efforts tohelp you understand the materials in this course by using many illustrativeexamples
bull I am always willing to answer your questions So please do not hesitate tocome to me whenever you have any
bull My contact information
Office HH-2016Office hour MTW 1000-1130 (or by appointment)Phone 864-4321Email xswang4gmailcom
Lecture Notes for Math 1000 First Previous Next Last 6
Outline
bull Textbook (either of the following two)
1 Calculus Early Transcendentals with WebAssign Access Card (bundle) byJon Rogawski OR
2 Math 1000 1001 Course Notes by Bruce Watson +Calculus Early Transcendentals WebAssign Card by Jon Rogawski
bull Topics to be covered limits and continuity differentiation and applications ofdifferentiation
bull Prerequisite Math 1090 or a combination of placement test and high schoolMathematics scores acceptable to the department
bull Marks 55 Final Exam 30 In-class tests (three tests with 10 each) 75WebAssign 75 Assignments
Lecture Notes for Math 1000 First Previous Next Last 7
Mathematics Placement Test
bull Students who are planning to do Math 1000 for the first time must write theMathematics Placement Test
bull The test will be administered for the last time this semester on Sep 11(Tuesday) at 1900 in HH-3017
bull Failure to write the MPT will result in deregistration from the course
bull The mark required to qualify for Math 1000 is 85 with Academic math 3204 or75 with Advanced math 3205
bull A synopsis of the MPT is available on the shelf (adjacent to HH-3009) acrossthe corridor from the General Office or online athttpwwwmuncamathmptsynopsis
Lecture Notes for Math 1000 First Previous Next Last 8
Assignments
bull Homework assignment must be handed in no later than 1400 on the due dateThey may be submitted in class or placed in the marking box Late assignmentwill NOT be marked
bull Assignments should be submitted on loose leaf 85rdquotimes 11rdquo paper stapled inthe upper left corner written on one side only with problems done in orderThey should not be placed in folders or any other container Assignmentsshould include a cover page with your name and student number the name ofthe course and the assignment number
bull If you are unable to submit an assignment due to illness bereavement or otheracceptable reason please provide me with appropriate documentation (egdoctorrsquos note death notice) and I will average together your remainingassignments to create a mark out of 75
Lecture Notes for Math 1000 First Previous Next Last 9
WebAssign
bull Website httpwwwmathmuncawebassign
bull The above website contains complete instructions for signing up for WebAssignand you should read it fully
bull In order to fully activate your WebAssign account you will need to purchase aWebAssign access code from the University Bookstore by September 18th
bull You MUST use your MUN email address when signing up for WebAssign
bull Should you have further questions with WebAssign please contact theWebAssign administrator Dr Sullivan (shannonmunca)
Lecture Notes for Math 1000 First Previous Next Last 10
Tests and exam
bull No notes textbooks calculators or any electronic communications device arepermitted during any test or final examination
bull There will be no make-up for a missed in-class test Upon presentation ofdocumentation of a valid excuse the corresponding percentage of the finalmark will be added to the final exam With no presentation of suchdocumentation a grade of zero will be entered for the missed test
bull Tentative dates for three in-class tests (will be confirmed in class)
1 Sep 28 Friday2 Oct 19 Friday3 Nov 09 Friday
Lecture Notes for Math 1000 First Previous Next Last 11
Supplementary exams
The Department of Mathematics and Statistics offers supplementary examinationsto students satisfying all of the following
bull the student is in clear academic standing
bull the student has a passing term mark and
bull the studentrsquos final grade is 45 to 49
Lecture Notes for Math 1000 First Previous Next Last 12
Whenever you need help
bull Math Help Center (HH-3015) stating from Sep 10 (Monday)
1000-1600 Monday Tuesday Wednesday and Thursday0900-1300 Friday
bull Office hour (HH-2016) 1000-1130 Monday Tuesday and Wednesday
bull Email xswang4gmailcom
bull Office phone number 864-4321
bull I am always willing to help you -)
Lecture Notes for Math 1000 First Previous Next Last 13
Niagara Falls ON
Lecture Notes for Math 1000 First Previous Next Last 14
St John River NB
Lecture Notes for Math 1000 First Previous Next Last 15
Difference between the falls and the river
bull The river has no jump It is continuous
bull The falls has a jump It is discontinuous
bull Question how to distinguish between continuity and discontinuity
bull Answer with the aid of limits
bull Remark Limits help us define continuity
Lecture Notes for Math 1000 First Previous Next Last 16
Continuity and discontinuity
The slides are continuous The stairs are discontinuous
Lecture Notes for Math 1000 First Previous Next Last 17
Discontinuity the unfinished bridge
The function is not defined at the discontinuous point
Lecture Notes for Math 1000 First Previous Next Last 18
Discontinuity the broken bridge
The limits from both sides do not match
Lecture Notes for Math 1000 First Previous Next Last 19
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
What can you benefit from me
bull I will show you that mathematics is not impossible I will try my best efforts tohelp you understand the materials in this course by using many illustrativeexamples
bull I am always willing to answer your questions So please do not hesitate tocome to me whenever you have any
bull My contact information
Office HH-2016Office hour MTW 1000-1130 (or by appointment)Phone 864-4321Email xswang4gmailcom
Lecture Notes for Math 1000 First Previous Next Last 6
Outline
bull Textbook (either of the following two)
1 Calculus Early Transcendentals with WebAssign Access Card (bundle) byJon Rogawski OR
2 Math 1000 1001 Course Notes by Bruce Watson +Calculus Early Transcendentals WebAssign Card by Jon Rogawski
bull Topics to be covered limits and continuity differentiation and applications ofdifferentiation
bull Prerequisite Math 1090 or a combination of placement test and high schoolMathematics scores acceptable to the department
bull Marks 55 Final Exam 30 In-class tests (three tests with 10 each) 75WebAssign 75 Assignments
Lecture Notes for Math 1000 First Previous Next Last 7
Mathematics Placement Test
bull Students who are planning to do Math 1000 for the first time must write theMathematics Placement Test
bull The test will be administered for the last time this semester on Sep 11(Tuesday) at 1900 in HH-3017
bull Failure to write the MPT will result in deregistration from the course
bull The mark required to qualify for Math 1000 is 85 with Academic math 3204 or75 with Advanced math 3205
bull A synopsis of the MPT is available on the shelf (adjacent to HH-3009) acrossthe corridor from the General Office or online athttpwwwmuncamathmptsynopsis
Lecture Notes for Math 1000 First Previous Next Last 8
Assignments
bull Homework assignment must be handed in no later than 1400 on the due dateThey may be submitted in class or placed in the marking box Late assignmentwill NOT be marked
bull Assignments should be submitted on loose leaf 85rdquotimes 11rdquo paper stapled inthe upper left corner written on one side only with problems done in orderThey should not be placed in folders or any other container Assignmentsshould include a cover page with your name and student number the name ofthe course and the assignment number
bull If you are unable to submit an assignment due to illness bereavement or otheracceptable reason please provide me with appropriate documentation (egdoctorrsquos note death notice) and I will average together your remainingassignments to create a mark out of 75
Lecture Notes for Math 1000 First Previous Next Last 9
WebAssign
bull Website httpwwwmathmuncawebassign
bull The above website contains complete instructions for signing up for WebAssignand you should read it fully
bull In order to fully activate your WebAssign account you will need to purchase aWebAssign access code from the University Bookstore by September 18th
bull You MUST use your MUN email address when signing up for WebAssign
bull Should you have further questions with WebAssign please contact theWebAssign administrator Dr Sullivan (shannonmunca)
Lecture Notes for Math 1000 First Previous Next Last 10
Tests and exam
bull No notes textbooks calculators or any electronic communications device arepermitted during any test or final examination
bull There will be no make-up for a missed in-class test Upon presentation ofdocumentation of a valid excuse the corresponding percentage of the finalmark will be added to the final exam With no presentation of suchdocumentation a grade of zero will be entered for the missed test
bull Tentative dates for three in-class tests (will be confirmed in class)
1 Sep 28 Friday2 Oct 19 Friday3 Nov 09 Friday
Lecture Notes for Math 1000 First Previous Next Last 11
Supplementary exams
The Department of Mathematics and Statistics offers supplementary examinationsto students satisfying all of the following
bull the student is in clear academic standing
bull the student has a passing term mark and
bull the studentrsquos final grade is 45 to 49
Lecture Notes for Math 1000 First Previous Next Last 12
Whenever you need help
bull Math Help Center (HH-3015) stating from Sep 10 (Monday)
1000-1600 Monday Tuesday Wednesday and Thursday0900-1300 Friday
bull Office hour (HH-2016) 1000-1130 Monday Tuesday and Wednesday
bull Email xswang4gmailcom
bull Office phone number 864-4321
bull I am always willing to help you -)
Lecture Notes for Math 1000 First Previous Next Last 13
Niagara Falls ON
Lecture Notes for Math 1000 First Previous Next Last 14
St John River NB
Lecture Notes for Math 1000 First Previous Next Last 15
Difference between the falls and the river
bull The river has no jump It is continuous
bull The falls has a jump It is discontinuous
bull Question how to distinguish between continuity and discontinuity
bull Answer with the aid of limits
bull Remark Limits help us define continuity
Lecture Notes for Math 1000 First Previous Next Last 16
Continuity and discontinuity
The slides are continuous The stairs are discontinuous
Lecture Notes for Math 1000 First Previous Next Last 17
Discontinuity the unfinished bridge
The function is not defined at the discontinuous point
Lecture Notes for Math 1000 First Previous Next Last 18
Discontinuity the broken bridge
The limits from both sides do not match
Lecture Notes for Math 1000 First Previous Next Last 19
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Outline
bull Textbook (either of the following two)
1 Calculus Early Transcendentals with WebAssign Access Card (bundle) byJon Rogawski OR
2 Math 1000 1001 Course Notes by Bruce Watson +Calculus Early Transcendentals WebAssign Card by Jon Rogawski
bull Topics to be covered limits and continuity differentiation and applications ofdifferentiation
bull Prerequisite Math 1090 or a combination of placement test and high schoolMathematics scores acceptable to the department
bull Marks 55 Final Exam 30 In-class tests (three tests with 10 each) 75WebAssign 75 Assignments
Lecture Notes for Math 1000 First Previous Next Last 7
Mathematics Placement Test
bull Students who are planning to do Math 1000 for the first time must write theMathematics Placement Test
bull The test will be administered for the last time this semester on Sep 11(Tuesday) at 1900 in HH-3017
bull Failure to write the MPT will result in deregistration from the course
bull The mark required to qualify for Math 1000 is 85 with Academic math 3204 or75 with Advanced math 3205
bull A synopsis of the MPT is available on the shelf (adjacent to HH-3009) acrossthe corridor from the General Office or online athttpwwwmuncamathmptsynopsis
Lecture Notes for Math 1000 First Previous Next Last 8
Assignments
bull Homework assignment must be handed in no later than 1400 on the due dateThey may be submitted in class or placed in the marking box Late assignmentwill NOT be marked
bull Assignments should be submitted on loose leaf 85rdquotimes 11rdquo paper stapled inthe upper left corner written on one side only with problems done in orderThey should not be placed in folders or any other container Assignmentsshould include a cover page with your name and student number the name ofthe course and the assignment number
bull If you are unable to submit an assignment due to illness bereavement or otheracceptable reason please provide me with appropriate documentation (egdoctorrsquos note death notice) and I will average together your remainingassignments to create a mark out of 75
Lecture Notes for Math 1000 First Previous Next Last 9
WebAssign
bull Website httpwwwmathmuncawebassign
bull The above website contains complete instructions for signing up for WebAssignand you should read it fully
bull In order to fully activate your WebAssign account you will need to purchase aWebAssign access code from the University Bookstore by September 18th
bull You MUST use your MUN email address when signing up for WebAssign
bull Should you have further questions with WebAssign please contact theWebAssign administrator Dr Sullivan (shannonmunca)
Lecture Notes for Math 1000 First Previous Next Last 10
Tests and exam
bull No notes textbooks calculators or any electronic communications device arepermitted during any test or final examination
bull There will be no make-up for a missed in-class test Upon presentation ofdocumentation of a valid excuse the corresponding percentage of the finalmark will be added to the final exam With no presentation of suchdocumentation a grade of zero will be entered for the missed test
bull Tentative dates for three in-class tests (will be confirmed in class)
1 Sep 28 Friday2 Oct 19 Friday3 Nov 09 Friday
Lecture Notes for Math 1000 First Previous Next Last 11
Supplementary exams
The Department of Mathematics and Statistics offers supplementary examinationsto students satisfying all of the following
bull the student is in clear academic standing
bull the student has a passing term mark and
bull the studentrsquos final grade is 45 to 49
Lecture Notes for Math 1000 First Previous Next Last 12
Whenever you need help
bull Math Help Center (HH-3015) stating from Sep 10 (Monday)
1000-1600 Monday Tuesday Wednesday and Thursday0900-1300 Friday
bull Office hour (HH-2016) 1000-1130 Monday Tuesday and Wednesday
bull Email xswang4gmailcom
bull Office phone number 864-4321
bull I am always willing to help you -)
Lecture Notes for Math 1000 First Previous Next Last 13
Niagara Falls ON
Lecture Notes for Math 1000 First Previous Next Last 14
St John River NB
Lecture Notes for Math 1000 First Previous Next Last 15
Difference between the falls and the river
bull The river has no jump It is continuous
bull The falls has a jump It is discontinuous
bull Question how to distinguish between continuity and discontinuity
bull Answer with the aid of limits
bull Remark Limits help us define continuity
Lecture Notes for Math 1000 First Previous Next Last 16
Continuity and discontinuity
The slides are continuous The stairs are discontinuous
Lecture Notes for Math 1000 First Previous Next Last 17
Discontinuity the unfinished bridge
The function is not defined at the discontinuous point
Lecture Notes for Math 1000 First Previous Next Last 18
Discontinuity the broken bridge
The limits from both sides do not match
Lecture Notes for Math 1000 First Previous Next Last 19
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Mathematics Placement Test
bull Students who are planning to do Math 1000 for the first time must write theMathematics Placement Test
bull The test will be administered for the last time this semester on Sep 11(Tuesday) at 1900 in HH-3017
bull Failure to write the MPT will result in deregistration from the course
bull The mark required to qualify for Math 1000 is 85 with Academic math 3204 or75 with Advanced math 3205
bull A synopsis of the MPT is available on the shelf (adjacent to HH-3009) acrossthe corridor from the General Office or online athttpwwwmuncamathmptsynopsis
Lecture Notes for Math 1000 First Previous Next Last 8
Assignments
bull Homework assignment must be handed in no later than 1400 on the due dateThey may be submitted in class or placed in the marking box Late assignmentwill NOT be marked
bull Assignments should be submitted on loose leaf 85rdquotimes 11rdquo paper stapled inthe upper left corner written on one side only with problems done in orderThey should not be placed in folders or any other container Assignmentsshould include a cover page with your name and student number the name ofthe course and the assignment number
bull If you are unable to submit an assignment due to illness bereavement or otheracceptable reason please provide me with appropriate documentation (egdoctorrsquos note death notice) and I will average together your remainingassignments to create a mark out of 75
Lecture Notes for Math 1000 First Previous Next Last 9
WebAssign
bull Website httpwwwmathmuncawebassign
bull The above website contains complete instructions for signing up for WebAssignand you should read it fully
bull In order to fully activate your WebAssign account you will need to purchase aWebAssign access code from the University Bookstore by September 18th
bull You MUST use your MUN email address when signing up for WebAssign
bull Should you have further questions with WebAssign please contact theWebAssign administrator Dr Sullivan (shannonmunca)
Lecture Notes for Math 1000 First Previous Next Last 10
Tests and exam
bull No notes textbooks calculators or any electronic communications device arepermitted during any test or final examination
bull There will be no make-up for a missed in-class test Upon presentation ofdocumentation of a valid excuse the corresponding percentage of the finalmark will be added to the final exam With no presentation of suchdocumentation a grade of zero will be entered for the missed test
bull Tentative dates for three in-class tests (will be confirmed in class)
1 Sep 28 Friday2 Oct 19 Friday3 Nov 09 Friday
Lecture Notes for Math 1000 First Previous Next Last 11
Supplementary exams
The Department of Mathematics and Statistics offers supplementary examinationsto students satisfying all of the following
bull the student is in clear academic standing
bull the student has a passing term mark and
bull the studentrsquos final grade is 45 to 49
Lecture Notes for Math 1000 First Previous Next Last 12
Whenever you need help
bull Math Help Center (HH-3015) stating from Sep 10 (Monday)
1000-1600 Monday Tuesday Wednesday and Thursday0900-1300 Friday
bull Office hour (HH-2016) 1000-1130 Monday Tuesday and Wednesday
bull Email xswang4gmailcom
bull Office phone number 864-4321
bull I am always willing to help you -)
Lecture Notes for Math 1000 First Previous Next Last 13
Niagara Falls ON
Lecture Notes for Math 1000 First Previous Next Last 14
St John River NB
Lecture Notes for Math 1000 First Previous Next Last 15
Difference between the falls and the river
bull The river has no jump It is continuous
bull The falls has a jump It is discontinuous
bull Question how to distinguish between continuity and discontinuity
bull Answer with the aid of limits
bull Remark Limits help us define continuity
Lecture Notes for Math 1000 First Previous Next Last 16
Continuity and discontinuity
The slides are continuous The stairs are discontinuous
Lecture Notes for Math 1000 First Previous Next Last 17
Discontinuity the unfinished bridge
The function is not defined at the discontinuous point
Lecture Notes for Math 1000 First Previous Next Last 18
Discontinuity the broken bridge
The limits from both sides do not match
Lecture Notes for Math 1000 First Previous Next Last 19
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Assignments
bull Homework assignment must be handed in no later than 1400 on the due dateThey may be submitted in class or placed in the marking box Late assignmentwill NOT be marked
bull Assignments should be submitted on loose leaf 85rdquotimes 11rdquo paper stapled inthe upper left corner written on one side only with problems done in orderThey should not be placed in folders or any other container Assignmentsshould include a cover page with your name and student number the name ofthe course and the assignment number
bull If you are unable to submit an assignment due to illness bereavement or otheracceptable reason please provide me with appropriate documentation (egdoctorrsquos note death notice) and I will average together your remainingassignments to create a mark out of 75
Lecture Notes for Math 1000 First Previous Next Last 9
WebAssign
bull Website httpwwwmathmuncawebassign
bull The above website contains complete instructions for signing up for WebAssignand you should read it fully
bull In order to fully activate your WebAssign account you will need to purchase aWebAssign access code from the University Bookstore by September 18th
bull You MUST use your MUN email address when signing up for WebAssign
bull Should you have further questions with WebAssign please contact theWebAssign administrator Dr Sullivan (shannonmunca)
Lecture Notes for Math 1000 First Previous Next Last 10
Tests and exam
bull No notes textbooks calculators or any electronic communications device arepermitted during any test or final examination
bull There will be no make-up for a missed in-class test Upon presentation ofdocumentation of a valid excuse the corresponding percentage of the finalmark will be added to the final exam With no presentation of suchdocumentation a grade of zero will be entered for the missed test
bull Tentative dates for three in-class tests (will be confirmed in class)
1 Sep 28 Friday2 Oct 19 Friday3 Nov 09 Friday
Lecture Notes for Math 1000 First Previous Next Last 11
Supplementary exams
The Department of Mathematics and Statistics offers supplementary examinationsto students satisfying all of the following
bull the student is in clear academic standing
bull the student has a passing term mark and
bull the studentrsquos final grade is 45 to 49
Lecture Notes for Math 1000 First Previous Next Last 12
Whenever you need help
bull Math Help Center (HH-3015) stating from Sep 10 (Monday)
1000-1600 Monday Tuesday Wednesday and Thursday0900-1300 Friday
bull Office hour (HH-2016) 1000-1130 Monday Tuesday and Wednesday
bull Email xswang4gmailcom
bull Office phone number 864-4321
bull I am always willing to help you -)
Lecture Notes for Math 1000 First Previous Next Last 13
Niagara Falls ON
Lecture Notes for Math 1000 First Previous Next Last 14
St John River NB
Lecture Notes for Math 1000 First Previous Next Last 15
Difference between the falls and the river
bull The river has no jump It is continuous
bull The falls has a jump It is discontinuous
bull Question how to distinguish between continuity and discontinuity
bull Answer with the aid of limits
bull Remark Limits help us define continuity
Lecture Notes for Math 1000 First Previous Next Last 16
Continuity and discontinuity
The slides are continuous The stairs are discontinuous
Lecture Notes for Math 1000 First Previous Next Last 17
Discontinuity the unfinished bridge
The function is not defined at the discontinuous point
Lecture Notes for Math 1000 First Previous Next Last 18
Discontinuity the broken bridge
The limits from both sides do not match
Lecture Notes for Math 1000 First Previous Next Last 19
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
WebAssign
bull Website httpwwwmathmuncawebassign
bull The above website contains complete instructions for signing up for WebAssignand you should read it fully
bull In order to fully activate your WebAssign account you will need to purchase aWebAssign access code from the University Bookstore by September 18th
bull You MUST use your MUN email address when signing up for WebAssign
bull Should you have further questions with WebAssign please contact theWebAssign administrator Dr Sullivan (shannonmunca)
Lecture Notes for Math 1000 First Previous Next Last 10
Tests and exam
bull No notes textbooks calculators or any electronic communications device arepermitted during any test or final examination
bull There will be no make-up for a missed in-class test Upon presentation ofdocumentation of a valid excuse the corresponding percentage of the finalmark will be added to the final exam With no presentation of suchdocumentation a grade of zero will be entered for the missed test
bull Tentative dates for three in-class tests (will be confirmed in class)
1 Sep 28 Friday2 Oct 19 Friday3 Nov 09 Friday
Lecture Notes for Math 1000 First Previous Next Last 11
Supplementary exams
The Department of Mathematics and Statistics offers supplementary examinationsto students satisfying all of the following
bull the student is in clear academic standing
bull the student has a passing term mark and
bull the studentrsquos final grade is 45 to 49
Lecture Notes for Math 1000 First Previous Next Last 12
Whenever you need help
bull Math Help Center (HH-3015) stating from Sep 10 (Monday)
1000-1600 Monday Tuesday Wednesday and Thursday0900-1300 Friday
bull Office hour (HH-2016) 1000-1130 Monday Tuesday and Wednesday
bull Email xswang4gmailcom
bull Office phone number 864-4321
bull I am always willing to help you -)
Lecture Notes for Math 1000 First Previous Next Last 13
Niagara Falls ON
Lecture Notes for Math 1000 First Previous Next Last 14
St John River NB
Lecture Notes for Math 1000 First Previous Next Last 15
Difference between the falls and the river
bull The river has no jump It is continuous
bull The falls has a jump It is discontinuous
bull Question how to distinguish between continuity and discontinuity
bull Answer with the aid of limits
bull Remark Limits help us define continuity
Lecture Notes for Math 1000 First Previous Next Last 16
Continuity and discontinuity
The slides are continuous The stairs are discontinuous
Lecture Notes for Math 1000 First Previous Next Last 17
Discontinuity the unfinished bridge
The function is not defined at the discontinuous point
Lecture Notes for Math 1000 First Previous Next Last 18
Discontinuity the broken bridge
The limits from both sides do not match
Lecture Notes for Math 1000 First Previous Next Last 19
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Tests and exam
bull No notes textbooks calculators or any electronic communications device arepermitted during any test or final examination
bull There will be no make-up for a missed in-class test Upon presentation ofdocumentation of a valid excuse the corresponding percentage of the finalmark will be added to the final exam With no presentation of suchdocumentation a grade of zero will be entered for the missed test
bull Tentative dates for three in-class tests (will be confirmed in class)
1 Sep 28 Friday2 Oct 19 Friday3 Nov 09 Friday
Lecture Notes for Math 1000 First Previous Next Last 11
Supplementary exams
The Department of Mathematics and Statistics offers supplementary examinationsto students satisfying all of the following
bull the student is in clear academic standing
bull the student has a passing term mark and
bull the studentrsquos final grade is 45 to 49
Lecture Notes for Math 1000 First Previous Next Last 12
Whenever you need help
bull Math Help Center (HH-3015) stating from Sep 10 (Monday)
1000-1600 Monday Tuesday Wednesday and Thursday0900-1300 Friday
bull Office hour (HH-2016) 1000-1130 Monday Tuesday and Wednesday
bull Email xswang4gmailcom
bull Office phone number 864-4321
bull I am always willing to help you -)
Lecture Notes for Math 1000 First Previous Next Last 13
Niagara Falls ON
Lecture Notes for Math 1000 First Previous Next Last 14
St John River NB
Lecture Notes for Math 1000 First Previous Next Last 15
Difference between the falls and the river
bull The river has no jump It is continuous
bull The falls has a jump It is discontinuous
bull Question how to distinguish between continuity and discontinuity
bull Answer with the aid of limits
bull Remark Limits help us define continuity
Lecture Notes for Math 1000 First Previous Next Last 16
Continuity and discontinuity
The slides are continuous The stairs are discontinuous
Lecture Notes for Math 1000 First Previous Next Last 17
Discontinuity the unfinished bridge
The function is not defined at the discontinuous point
Lecture Notes for Math 1000 First Previous Next Last 18
Discontinuity the broken bridge
The limits from both sides do not match
Lecture Notes for Math 1000 First Previous Next Last 19
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Supplementary exams
The Department of Mathematics and Statistics offers supplementary examinationsto students satisfying all of the following
bull the student is in clear academic standing
bull the student has a passing term mark and
bull the studentrsquos final grade is 45 to 49
Lecture Notes for Math 1000 First Previous Next Last 12
Whenever you need help
bull Math Help Center (HH-3015) stating from Sep 10 (Monday)
1000-1600 Monday Tuesday Wednesday and Thursday0900-1300 Friday
bull Office hour (HH-2016) 1000-1130 Monday Tuesday and Wednesday
bull Email xswang4gmailcom
bull Office phone number 864-4321
bull I am always willing to help you -)
Lecture Notes for Math 1000 First Previous Next Last 13
Niagara Falls ON
Lecture Notes for Math 1000 First Previous Next Last 14
St John River NB
Lecture Notes for Math 1000 First Previous Next Last 15
Difference between the falls and the river
bull The river has no jump It is continuous
bull The falls has a jump It is discontinuous
bull Question how to distinguish between continuity and discontinuity
bull Answer with the aid of limits
bull Remark Limits help us define continuity
Lecture Notes for Math 1000 First Previous Next Last 16
Continuity and discontinuity
The slides are continuous The stairs are discontinuous
Lecture Notes for Math 1000 First Previous Next Last 17
Discontinuity the unfinished bridge
The function is not defined at the discontinuous point
Lecture Notes for Math 1000 First Previous Next Last 18
Discontinuity the broken bridge
The limits from both sides do not match
Lecture Notes for Math 1000 First Previous Next Last 19
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Whenever you need help
bull Math Help Center (HH-3015) stating from Sep 10 (Monday)
1000-1600 Monday Tuesday Wednesday and Thursday0900-1300 Friday
bull Office hour (HH-2016) 1000-1130 Monday Tuesday and Wednesday
bull Email xswang4gmailcom
bull Office phone number 864-4321
bull I am always willing to help you -)
Lecture Notes for Math 1000 First Previous Next Last 13
Niagara Falls ON
Lecture Notes for Math 1000 First Previous Next Last 14
St John River NB
Lecture Notes for Math 1000 First Previous Next Last 15
Difference between the falls and the river
bull The river has no jump It is continuous
bull The falls has a jump It is discontinuous
bull Question how to distinguish between continuity and discontinuity
bull Answer with the aid of limits
bull Remark Limits help us define continuity
Lecture Notes for Math 1000 First Previous Next Last 16
Continuity and discontinuity
The slides are continuous The stairs are discontinuous
Lecture Notes for Math 1000 First Previous Next Last 17
Discontinuity the unfinished bridge
The function is not defined at the discontinuous point
Lecture Notes for Math 1000 First Previous Next Last 18
Discontinuity the broken bridge
The limits from both sides do not match
Lecture Notes for Math 1000 First Previous Next Last 19
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Niagara Falls ON
Lecture Notes for Math 1000 First Previous Next Last 14
St John River NB
Lecture Notes for Math 1000 First Previous Next Last 15
Difference between the falls and the river
bull The river has no jump It is continuous
bull The falls has a jump It is discontinuous
bull Question how to distinguish between continuity and discontinuity
bull Answer with the aid of limits
bull Remark Limits help us define continuity
Lecture Notes for Math 1000 First Previous Next Last 16
Continuity and discontinuity
The slides are continuous The stairs are discontinuous
Lecture Notes for Math 1000 First Previous Next Last 17
Discontinuity the unfinished bridge
The function is not defined at the discontinuous point
Lecture Notes for Math 1000 First Previous Next Last 18
Discontinuity the broken bridge
The limits from both sides do not match
Lecture Notes for Math 1000 First Previous Next Last 19
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
St John River NB
Lecture Notes for Math 1000 First Previous Next Last 15
Difference between the falls and the river
bull The river has no jump It is continuous
bull The falls has a jump It is discontinuous
bull Question how to distinguish between continuity and discontinuity
bull Answer with the aid of limits
bull Remark Limits help us define continuity
Lecture Notes for Math 1000 First Previous Next Last 16
Continuity and discontinuity
The slides are continuous The stairs are discontinuous
Lecture Notes for Math 1000 First Previous Next Last 17
Discontinuity the unfinished bridge
The function is not defined at the discontinuous point
Lecture Notes for Math 1000 First Previous Next Last 18
Discontinuity the broken bridge
The limits from both sides do not match
Lecture Notes for Math 1000 First Previous Next Last 19
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Difference between the falls and the river
bull The river has no jump It is continuous
bull The falls has a jump It is discontinuous
bull Question how to distinguish between continuity and discontinuity
bull Answer with the aid of limits
bull Remark Limits help us define continuity
Lecture Notes for Math 1000 First Previous Next Last 16
Continuity and discontinuity
The slides are continuous The stairs are discontinuous
Lecture Notes for Math 1000 First Previous Next Last 17
Discontinuity the unfinished bridge
The function is not defined at the discontinuous point
Lecture Notes for Math 1000 First Previous Next Last 18
Discontinuity the broken bridge
The limits from both sides do not match
Lecture Notes for Math 1000 First Previous Next Last 19
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Continuity and discontinuity
The slides are continuous The stairs are discontinuous
Lecture Notes for Math 1000 First Previous Next Last 17
Discontinuity the unfinished bridge
The function is not defined at the discontinuous point
Lecture Notes for Math 1000 First Previous Next Last 18
Discontinuity the broken bridge
The limits from both sides do not match
Lecture Notes for Math 1000 First Previous Next Last 19
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Discontinuity the unfinished bridge
The function is not defined at the discontinuous point
Lecture Notes for Math 1000 First Previous Next Last 18
Discontinuity the broken bridge
The limits from both sides do not match
Lecture Notes for Math 1000 First Previous Next Last 19
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Discontinuity the broken bridge
The limits from both sides do not match
Lecture Notes for Math 1000 First Previous Next Last 19
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Graphical investigation of f(x) = sin xx
x
fHxL=
sinHxLx
1
f(x) = sin xx approaches 1 when x is close (but not equal) to 0
Lecture Notes for Math 1000 First Previous Next Last 21
Definition of limits
bull f(x) is defined for all x near c but not necessarily at c itself
bull |f(x)minus L| becomes arbitrarily small when x is any number sufficiently close(but not equal) to c
bull We say that the limit of f(x) as x approaches c is equal to L
bull We writelimxrarrc
f(x) = L
bull We also say that f(x)rarr L (f(x) approaches or converges to L) as xrarr c (xtends to c)
Lecture Notes for Math 1000 First Previous Next Last 22
Limits of two simple functions
For any constant k and c we have
limxrarrc
k = k and limxrarrc
x = c
x
f HxL=k
k
c
x
f HxL=x
c
c
Lecture Notes for Math 1000 First Previous Next Last 23
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Definition of limits
bull f(x) is defined for all x near c but not necessarily at c itself
bull |f(x)minus L| becomes arbitrarily small when x is any number sufficiently close(but not equal) to c
bull We say that the limit of f(x) as x approaches c is equal to L
bull We writelimxrarrc
f(x) = L
bull We also say that f(x)rarr L (f(x) approaches or converges to L) as xrarr c (xtends to c)
Lecture Notes for Math 1000 First Previous Next Last 22
Limits of two simple functions
For any constant k and c we have
limxrarrc
k = k and limxrarrc
x = c
x
f HxL=k
k
c
x
f HxL=x
c
c
Lecture Notes for Math 1000 First Previous Next Last 23
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Limits of two simple functions
For any constant k and c we have
limxrarrc
k = k and limxrarrc
x = c
x
f HxL=k
k
c
x
f HxL=x
c
c
Lecture Notes for Math 1000 First Previous Next Last 23
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Graphical investigation of limxrarr1
xminus1radicxminus1
x
fHxL=x - 1
x - 1
2
1
limxrarr1
xminus1radicxminus1 = 2
Lecture Notes for Math 1000 First Previous Next Last 25
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Graphical investigation of limxrarr1
x2
x
fHxL=x2
1
1
limxrarr1
x2 = 1
Lecture Notes for Math 1000 First Previous Next Last 27
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Graphical investigation of limxrarr0
exminus1x
x
fHxL=atildex - 1
x
1
limxrarr0
exminus1x = 1
Lecture Notes for Math 1000 First Previous Next Last 29
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Graphical investigation of limxrarr0
cosx
x
fHxL=cosHxL
1
limxrarr0
cosx = 1
Lecture Notes for Math 1000 First Previous Next Last 31
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Graphical investigation of limxrarr0
sin 1x
x
fHxL=sin1
x
limxrarr0
sin 1x does not exist
Lecture Notes for Math 1000 First Previous Next Last 33
One-sided limits
bull Left-hand limit limxrarrcminus
f(x) = L if f(x) converges to L as x approaches c from
left-hand side
bull Right-hand limit limxrarrc+
f(x) = L if f(x) converges to L as x approaches c
from right-hand side
bull Theorem limxrarrc
f(x) = L if and only if both limxrarrcminus
f(x) = L and limxrarrc+
f(x) = L
are satisfied
Lecture Notes for Math 1000 First Previous Next Last 34
The absolute value function f(x) = |x|
x
fHxL= xcurren
-1-2-3 1 2 3
1
2
3
Lecture Notes for Math 1000 First Previous Next Last 35
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
One-sided limits
bull Left-hand limit limxrarrcminus
f(x) = L if f(x) converges to L as x approaches c from
left-hand side
bull Right-hand limit limxrarrc+
f(x) = L if f(x) converges to L as x approaches c
from right-hand side
bull Theorem limxrarrc
f(x) = L if and only if both limxrarrcminus
f(x) = L and limxrarrc+
f(x) = L
are satisfied
Lecture Notes for Math 1000 First Previous Next Last 34
The absolute value function f(x) = |x|
x
fHxL= xcurren
-1-2-3 1 2 3
1
2
3
Lecture Notes for Math 1000 First Previous Next Last 35
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
The absolute value function f(x) = |x|
x
fHxL= xcurren
-1-2-3 1 2 3
1
2
3
Lecture Notes for Math 1000 First Previous Next Last 35
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
When x gt 0 we have |x| = x When x lt 0 we have |x| = minusx
Lecture Notes for Math 1000 First Previous Next Last 36
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
|x| and piecewise function
bull When x gt 0 we replace |x| by x So
2x+ |x|x+ 2|x|
=2x+x
x+2x=
3x
3x= 1
bull When x lt 0 we replace |x| by minusx So
2x+ |x|x+ 2|x|
=2xminusxxminus2x
=x
minusx= minus1
bull The function f(x) = 2x+|x|x+2|x| is a piecewise function
2x+ |x|x+ 2|x|
=
1 for x gt 0
minus1 for x lt 0
Lecture Notes for Math 1000 First Previous Next Last 37
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
When the limit is infinitybull If f(x) increases without bound as xrarr c then we write lim
xrarrcf(x) =infin
bull If f(x) tends to minusinfin (ie f(x) becomes negative and |f(x)| rarr infin) as xrarr cthen we write lim
xrarrcf(x) = minusinfin
bull If f(x)rarrinfin as x approaches c from the left-hand side (xrarr cminus) then wewrite lim
xrarrcminusf(x) =infin
bull If f(x)rarrinfin as x approaches c from the right-hand side (xrarr c+) then wewrite lim
xrarrc+f(x) =infin
bull If f(x)rarr minusinfin as xrarr cminus then we write limxrarrcminus
f(x) = minusinfin
bull If f(x)rarr minusinfin as xrarr c+ then we write limxrarrc+
f(x) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 38
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
The function f(x) = 1x
x
fHxL=
1
x
limxrarr0minus
1x = minusinfin lim
xrarr0+
1x =infin lim
xrarr0
1x does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 39
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
The function f(x) = 1x2
x
fHxL=
1
x2
limxrarr0minus
1x2 =infin lim
xrarr0+
1x2 =infin lim
xrarr0
1x2 =infin
Lecture Notes for Math 1000 First Previous Next Last 40
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
The function f(x) = lnx
x
fHxL=lnHxL
limxrarr0minus
lnx does NOT exist limxrarr0+
lnx = minusinfin limxrarr0
lnx does NOT exist
Lecture Notes for Math 1000 First Previous Next Last 41
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
The notation infin
bull The notation infin looks like a sideways 8
limxrarr8+
1
xminus 8=infin
bull Good mathematical skills
limxrarr2+
1
xminus 2=
2 times
limxrarr2+
1
xminus 2= 2 times
limxrarr2+
1
xminus 2=infin X
Lecture Notes for Math 1000 First Previous Next Last 42
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Basic limit laws
Assume that limxrarrc
f(x) and limxrarrc
g(x) exist Then
(i) Sum Lawlimxrarrc
(f(x) + g(x)) = limxrarrc
f(x) + limxrarrc
g(x)
(ii) Constant Multiple Law For any number k
limxrarrc
kf(x) = k limxrarrc
f(x)
(iii) Product Lawlimxrarrc
(f(x)g(x)) =(
limxrarrc
f(x))(
limxrarrc
g(x))
(iv) Quotient Law If limxrarrc
g(x) 6= 0 then
limxrarrc
f(x)
g(x)=
limxrarrc
f(x)
limxrarrc
g(x)
Lecture Notes for Math 1000 First Previous Next Last 43
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Basic limit laws
bull The Sum and Product Laws are valid for any finite number of functions Forexample assume that lim
xrarrcf1(x) lim
xrarrcf2(x) and lim
xrarrcf3(x) exist Then
limxrarrc
(f1(x) + f2(x) + f3(x)) = limxrarrc
f1(x) + limxrarrc
f2(x) + limxrarrc
f3(x)
limxrarrc
(f1(x)f2(x)f3(x)) =(
limxrarrc
f1(x))(
limxrarrc
f2(x))(
limxrarrc
f3(x))
bull The Sum Law and Constant Multiple Law imply Difference Law Assume thatlimxrarrc
f(x) and limxrarrc
g(x) exist Then
limxrarrc
(f(x)minus g(x)) = limxrarrc
f(x) + limxrarrc
(minusg(x)) = limxrarrc
f(x)minus limxrarrc
g(x)
bull To apply the Limit Laws we need to assume limxrarrc
f(x) and limxrarrc
g(x) exist
bull We have to do algebraic transformations before applying the Limit Laws
Lecture Notes for Math 1000 First Previous Next Last 44
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 45
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
The squeeze theorem
x
y uHxL
lHxL
fHxL
f(x) is NOT squeezed at x = 0 by l(x) and u(x)
Lecture Notes for Math 1000 First Previous Next Last 46
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
The squeeze theorem
If f(x) is squeezed at x = c by l(x) and u(x) namely
1 l(x) le f(x) le u(x) for all x close (but not equal) to c2 lim
xrarrcl(x) = lim
xrarrcu(x) = L
Then the limit limxrarrc
f(x) exists and limxrarrc
f(x) = L
The meatvegetable is squeezed by the two breads
Lecture Notes for Math 1000 First Previous Next Last 47
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
The squeeze theorem limxrarr0
x sin 1x = 0
x
y
uHxL=EgravexEgrave
lHxL=-EgravexEgrave
fHxL=x sin1
x
f(x) = x sin 1x is squeezed at x = 0 by l(x) = minus|x| and u(x) = |x|
Lecture Notes for Math 1000 First Previous Next Last 48
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Three techniques for evaluating limits and two formulas
bull Three techniques
1 Algebraic Transformation2 The Squeeze Theorem3 Change of Variable
bull Two formulas
limxrarr0
sinx
x= 1 and lim
xrarr0
1minus cosx
x= 0
Lecture Notes for Math 1000 First Previous Next Last 49
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Limits at infinity and asymptotes
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x increases withoutbound (xrarrinfin) then we write
limxrarrinfin
f(x) = L
bull If |f(x)minus L| becomes arbitrarily small (f(x)rarr L) as x decreases withoutbound (xrarr minusinfin) then we write
limxrarrminusinfin
f(x) = L
bull The horizontal line y = L is called a horizontal asymptote of f(x) if
limxrarrinfin
f(x) = L or limxrarrminusinfin
f(x) = L
bull The vertical line x = c is called a vertical asymptote of f(x) if the left-hand orright-hand limit of f(x) at x = c is equal to infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 50
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Limits at infinity
bull For any a gt 0 we have
limxrarrinfin
xminusa = 0 and limxrarrinfin
xa =infin
bull Three properties
1 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L then limxrarrinfin
(f(x)plusmn g(x)) =infin
2 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) =infin then limxrarrinfin
(f(x) + g(x)) =infin
3 If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L gt 0 then limxrarrinfin
(f(x)g(x)) =infin
If limxrarrinfin
f(x) =infin and limxrarrinfin
g(x) = L lt 0 then limxrarrinfin
(f(x)g(x)) = minusinfin
Lecture Notes for Math 1000 First Previous Next Last 51
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
x2 runs faster than x as xrarrinfin
x2 is the hare (rabbit) x is the tortoise (turtle) x2 runs faster than x as xrarrinfin
limxrarrinfin
(x2 minus x) =infin
Lecture Notes for Math 1000 First Previous Next Last 52
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Limits of polynomials at infinity
bull Transform the differencesum into a product
limxrarrinfin
(x2 minus x) = limxrarrinfin
x2(1minus xminus1) =infin
bull The leading term of a polynomial dominates when xrarrinfin namely if n ge 1and an 6= 0 then
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Limits of rational functions and limits at minusinfin
bull If xrarr minusinfin then we make a change of variable y = minusx (replace xrarr minusinfin byy rarrinfin and x by minusy)
limxrarrminusinfin
f(x) = limyrarrinfin
f(minusy)
Lecture Notes for Math 1000 First Previous Next Last 54
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Horizontal and vertical asymptotes
bull The horizontal asymptotes come from the limits at infinity (if exist)
bull The vertical asymptotes of a rational function come from the point when thedenominator of this rational function becomes zero
bull Steps in finding asymptotes of a rational function
1 Evaluate the limits at infin and minusinfin to obtain horizontal asymptotes2 Find the points when the denominator of this rational function becomes zero3 For each point found in the previous step evaluate the one-sided limits at
this point If one of the limits is infin or minusinfin then we obtain a verticalasymptote otherwise both one-sided limits are finite and this point doesNOT give a vertical asymptote
Lecture Notes for Math 1000 First Previous Next Last 55
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Continuity
Let f(x) be defined for x near c AND x = c We say f is continuous at x = c if
limxrarrc
f(x) = f(c)
Otherwise we say f is discontinuous at x = c
1 We say f has a removable discontinuity at x = c if
limxrarrc
f(x) 6= f(c)
2 We say f has a jump discontinuity at x = c if
limxrarrcminus
f(x) 6= limxrarrc+
f(x)
3 We say f has an infinite discontinuity at x = c if either or both theon-sided limit is infin or minusinfin
Lecture Notes for Math 1000 First Previous Next Last 56
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
One-sided continuity and laws of continuity
bull f(x) is called left-continuous if
limxrarrcminus
f(x) = f(c)
f(x) is called right-continuous if
limxrarrc+
f(x) = f(c)
bull (Laws of Continuity) If f(x) and g(x) are continuous at x = c Thenf(x)plusmn g(x) kf(x) f(x)g(x) are continuous at x = c If further g(c) 6= 0then f(x)g(x) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 57
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
An example
x
y
-1 1 2
-1
1
f(x) is continuous at x = 1 and discontinuous at x = minus1 0 2f(x) has an infinite discontinuity at x = minus1
a jump discontinuity at x = 0and a removable discontinuity at x = 2
f(x) is left-continuous (but NOT right-continuous) at x = 0
Lecture Notes for Math 1000 First Previous Next Last 58
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Basic functions inverse function and composite function
bull (Polynomial and rational functions) Let P (x) and Q(x) be polynomials Then
1 P (x) is continuous on the real line2 P (x)Q(x) is continuous at x = c if Q(c) 6= 0
bull (Basic functions)
1 f(x) = sinx and f(x) = cosx are continuous on the real line2 For b gt 0 f(x) = bx is continuous on the real line3 For b gt 0 and b 6= 1 f(x) = logb x is continuous for x gt 04 If n is a rational number then f(x) = x1n is continuous on its domain
bull (Inverse function) If f(x) is continuous on an interval I with range R and ifthe inverse fminus1(x) exists then fminus1(x) is continuous on R
bull (Composite function) If g(x) is continuous at x = c and if f(y) is continuousat y = g(c) then f(g(x)) is continuous at x = c
Lecture Notes for Math 1000 First Previous Next Last 59
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Rates of change
bull The average rate of change of a function y = f(x) over an interval [x0 x1] isdefined as
∆y
∆x=f(x1)minus f(x0)
x1 minus x0
bull The instantaneous rate of change of a function y = f(x) at x = x0 is definedas
limx1rarrx0
f(x1)minus f(x0)
x1 minus x0= lim
hrarr0
f(x0 + h)minus f(x0)
h
bull The average rate of change is equal to the slope of the secant line through(x0 f(x0)) and (x1 f(x1))
bull The instantaneous rate of change is equal to the slope of the tangent line atx = x0
Lecture Notes for Math 1000 First Previous Next Last 60
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Rates of change
(Loading Video)
The secant line (red) approaches the tangent line (green)The average rate of change approaches the instantaneous rate of change
Lecture Notes for Math 1000 First Previous Next Last 61
tangentavi
Media File (videoavi)
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Rates of change bubble gum
Lecture Notes for Math 1000 First Previous Next Last 62
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Rates of change bubble gum
bull The volume of the bubble is
V (r) =4
3πr3
bull The average ROC of bubble volume when the radius increases from r0 to r1 is
V (r1)minus V (r0)
r1 minus r0=
4
3π(r21 + r1r0 + r20)
bull The instantaneous ROC of bubble volume at r = r0 is
limr1rarrr0
V (r1)minus V (r0)
r1 minus r0= 4πr20
Lecture Notes for Math 1000 First Previous Next Last 63
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Rates of change throwing a ball up in the air
Lecture Notes for Math 1000 First Previous Next Last 64
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Rates of change throwing a ball up in the air
bull The height of the ball at time t is given by the displacement function
s(t) = 16tminus 16t2
bull The average ROC of height (average velocity) over [t0 t1] is
s(t1)minus s(t0)t1 minus t0
= 16minus 16(t1 + t0)
bull The instantaneous ROC of height (instantaneous velocity) at t = t0 is
limt1rarrt0
s(t1)minus s(t0)t1 minus t0
= 16minus 32t0
Lecture Notes for Math 1000 First Previous Next Last 65
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Derivative and tangent line
bull The derivative of a function f(x) at x = a is the limit of the differencequotient (if exists)
f prime(a) = limxrarra
f(x)minus f(a)
xminus a= lim
hrarr0
f(a+ h)minus f(a)
h
If f prime(a) exists then we say that f is differentiable at x = a
bull The tangent line to y = f(x) at x = a has the slope f prime(a) and the equation inpoint-slope form
y minus f(a) = f prime(a)(xminus a)
bull We say y = f(x) is differentiable in (a b) if f prime(x) exists for all x in (a b) Inthis case we view yprime = f prime(x) as a function defined on (a b)
Lecture Notes for Math 1000 First Previous Next Last 66
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Notations
bull Let y = f(x) then its derivative function is denoted by
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
For example if y = f(x) = xminus1 then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(xminus1) = minusxminus2
bull If y = f(x) is differentiable at x = a then we write
yprime(a) = f prime(a) =dy
dx
∣∣∣∣x=a
=df
dx
∣∣∣∣x=a
For example if y = f(x) = xminus1 and a = 1 then
yprime(1) = f prime(1) =dy
dx
∣∣∣∣x=1
=df
dx
∣∣∣∣x=1
=(minusxminus2
) ∣∣∣∣x=1
= minus1
Lecture Notes for Math 1000 First Previous Next Last 67
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Theorems
Let f(x) and g(x) be differentiable functions
bull The Power Rule(xa)prime = axaminus1
bull The Sum Rule(f plusmn g)prime = f prime plusmn gprime
bull The Constant Multiple Rule(cf)prime = cf prime
bull If f is differentiable at x = c then f is continuous at x = c
bull Remark If f is continuous at x = c It is NOT necessarily that f isdifferentiable at x = c (Counter example f(x) = |x| and c = 0)
Lecture Notes for Math 1000 First Previous Next Last 68
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
The product and quotient rules higher derivatives
bull The Product Rule(fg)prime = f primeg + fgprime
bull The Quotient Rule (f
g
)prime=f primeg minus fgprime
g2
bull Higher derivatives let y = f(x) then
yprime = f prime(x) =dy
dx=df
dx=
d
dx(f(x))
yprimeprime = f primeprime(x) =d
dx
(dy
dx
)=
d
dx
(dy
dx
)=d2y
dx2=d2f
dx2=
d
dx
(d
dx(f(x))
)yprimeprimeprime = f primeprimeprime(x) = y(3) = f (3)(x) =
d3y
dx3=d3f
dx3=
d
dx
(d
dx
(d
dx(f(x))
))Lecture Notes for Math 1000 First Previous Next Last 69
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Derivatives of trigonometric and exponential functions
bull Three basic formulas
d
dx(sinx) = cosx
d
dx(cosx) = minus sinx and
d
dx(ex) = ex
bull Express everything in terms of sinx and cosx and then apply derivative rules
d
dx(tanx) =
d
dx
(sinx
cosx
)=
1
cos2 x= sec2 x
d
dx(cotx) =
d
dx
(cosx
sinx
)= minus 1
sin2 x= minus csc2 x
d
dx(secx) =
d
dx
(1
cosx
)=
sinx
cos2 x= secx tanx
d
dx(cscx) =
d
dx
(1
sinx
)= minus cosx
sin2 x= minus cscx cotx
Lecture Notes for Math 1000 First Previous Next Last 70
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
The chain rule
bull Let u = g(x) be differentiable at x = x0 and y = f(u) be differentiable atu = u0 = g(x0) then y = f(g(x)) is differentiable at x = x0 and
dy
dx
∣∣∣∣x=x0
=dy
du
∣∣∣∣u=u0=g(x0)
times dudx
∣∣∣∣x=x0
bull We can also write
dy
dx=dy
du
du
dxor
d
dxf(g(x)) = f prime(g(x))gprime(x) or
d
dxf(u) = f prime(u)
du
dx
Lecture Notes for Math 1000 First Previous Next Last 71
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
The chain rule (special applications)
bull If g(x) is differentiable then
d
dx(g(x))a = a(g(x))aminus1gprime(x) and
d
dxeg(x) = gprime(x)eg(x)
bull If f(u) is differentiable then
d
dxf(kx+ b) = kf prime(kx+ b)
Especially if f(u) = eu then
(ekx+b)prime = kekx+b
bull If b gt 0 then(bx)prime = (ln b)bx
Lecture Notes for Math 1000 First Previous Next Last 72
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Implicit differentiation
bull Given an implicit function
y4 + xy = x3 minus x+ 2
bull Take derivative with respect to x on both side of the equation
d
dx(y4 + xy) =
d
dx(x3 minus x+ 2)
bull Apply the chain rule and other derivative rules to obtain
4y3dy
dx+ y + x
dy
dx= 3x2 minus 1
bull Solvedydx from the above equation
dy
dx=
3x2 minus 1minus y4y3 + x
Lecture Notes for Math 1000 First Previous Next Last 73
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Derivative of inverse function
bull If y = f(x) is differentiable at x = x0 and f prime(x0) 6= 0 Then then inversefunction x = g(y) = fminus1(y) is differentiable at y = y0 = f(x0) and
gprime(y0) =1
f prime(x0)=
1
f prime(g(y0))
bull Inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
Lecture Notes for Math 1000 First Previous Next Last 74
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
y = sinx and y = sinminus1 x
x
y=sinHxL
-Π 2
-1
1
Π 2x
y=sin-1HxL
-Π 2
-1
1
Π 2
[minusπ
2π
2
]sinminusminusminusminusminusminussinminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 75
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
y = cosx and y = cosminus1 x
x
y=cosHxL
Π
-1
1
Π 2
x
y=cos-1HxL
Π
-1 1
Π 2
[0 π]cosminusminusminusminusminusminuscosminus1
[minus1 1]
Lecture Notes for Math 1000 First Previous Next Last 76
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
y = tanx and y = tanminus1 x
x
y=tanHxL
-Π 2 Π 2 x
y=tan-1HxL
-Π 2
Π 2
(minusπ
2π
2
)tanminusminusminusminusminusminustanminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 77
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
y = cotx and y = cotminus1 x
x
y=cotHxL
ΠΠ 2
x
y=cot-1HxLΠ
Π 2
(0 π)cotminusminusminusminusminusminuscotminus1
(minusinfininfin)
Lecture Notes for Math 1000 First Previous Next Last 78
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
y = cscx and y = cscminus1 x
x
y=cscHxL
-Π 2
-1
1
Π 2 x
y=csc-1HxL
-Π 2
-11
Π 2
[minusπ
2 0)cup(
0π
2
]cscminusminusminusminusminusminuscscminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 79
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
y = secx and y = secminus1 x
x
y=secHxL
Π
-1
1
Π 2
x
y=sec-1HxLΠ
-1 1
Π 2
[0π
2
)cup(π
2 π]
secminusminusminusminusminusminussecminus1
(minusinfinminus1] cup [1infin)
Lecture Notes for Math 1000 First Previous Next Last 80
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Derivatives of inverse trigonometric functions
(sinminus1 y)prime =1
(sinx)prime=
1
cosx=
1radic1minus sin2 x
=1radic
1minus y2
(cosminus1 y)prime =1
(cosx)prime=
1
minus sinx=
1
minusradic
1minus cos2 x=
1
minusradic
1minus y2
(tanminus1 y)prime =1
(tanx)prime= cos2 x =
cos2 x
cos2 x+ sin2 x=
1
1 + tan2 x=
1
1 + y2
(cotminus1 y)prime =1
(cotx)prime= minus sin2 x = minus sin2 x
sin2 x+ cos2 x= minus 1
1 + cot2 x= minus 1
1 + y2
(secminus1 y)prime =1
(secx)prime=
cos2 x
sinx=
cos2 xradic1minus cos2 x
=1
y2radic
1minus (1y)2=
1
|y|radicy2 minus 1
(cscminus1 y)prime =1
(cscx)prime=minus sin2 x
cosx=
minus sin2 xradic1minus sin2 x
=minus1
y2radic
1minus (1y)2=
minus1
|y|radicy2 minus 1
Lecture Notes for Math 1000 First Previous Next Last 81
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Derivatives of logarithmic functions and hyperbolic functions
bull Logarithmic functions
(log x)prime =1
xand (log g(x))prime =
gprime(x)
g(x)
bull Hyperbolic sine and cosine functions
sinhx =ex minus eminusx
2and coshx =
ex + eminusx
2
bull Identitycosh2xminus sinh2x = 1
bull Derivatives(sinhx)prime = coshx and (coshx)prime = sinhx
Lecture Notes for Math 1000 First Previous Next Last 82
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Derivatives of hyperbolic functions
bull Hyperbolic tangent and cotangent functions
tanhx =sinhx
coshx=ex minus eminusx
ex + eminusxand cothx =
coshx
sinhx=ex + eminusx
ex minus eminusx
bull Derivatives
(tanhx)prime =
(sinhx
coshx
)prime=
(sinhx)prime(coshx)minus (sinhx)(coshx)prime
cosh2x
=(coshx)(coshx)minus (sinhx)(sinhx)
cosh2x=
1
cosh2x= sech2x
(cothx)prime =
(coshx
sinhx
)prime=
(coshx)prime(sinhx)minus (coshx)(sinhx)prime
sinh2x
=(sinhx)(sinhx)minus (coshx)(coshx)
sinh2x=minus1
sinh2x= minuscsch2x
Lecture Notes for Math 1000 First Previous Next Last 83
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Derivatives of hyperbolic functions
bull Hyperbolic secant and cosecant functions
sechx =1
coshx=
2
ex + eminusxand cschx =
1
sinhx=
2
ex minus eminusx
bull Derivatives
(sechx)prime =
(1
coshx
)prime=
(1)prime(coshx)minus (1)(coshx)prime
cosh2x=minussinhx
cosh2x= minustanhxsechx
(cschx)prime =
(1
sinhx
)prime=
(1)prime(sinhx)minus (1)(sinhx)prime
sinh2x=minuscoshx
sinh2x= minus cothxcschx
bull Express every hyperbolic function in terms of sinh and cosh
Lecture Notes for Math 1000 First Previous Next Last 84
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Absolute extrema
bull Let f(x) be defined on an interval I and let c isin I We say
1 f(c) is an absolute maximum if f(x) le f(c) for all x isin I2 f(c) is an absolute minimum if f(x) ge f(c) for all x isin I
bull If f(x) is continuous on the closed and bounded interval I = [a b] then f(x)has absolute extrema (maximum and minimum) on I
bull If f prime(c) is not defined or f prime(c) = 0 then c is called a critical point of f(x)
bull Let f(x) be continuous on the closed and bounded interval I = [a b] If f(c) isan absolute extremum (maximum or minimum) of f(x) on I then c is either acritical point or an end point
Lecture Notes for Math 1000 First Previous Next Last 85
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Relative extrema
bull Let f(x) be defined near x = c and x = c is not an end point
1 We say f(c) is a relative maximum if f(x) le f(c) for all x close to c2 We say f(c) is a relative minimum if f(x) ge f(c) for all x close to c
bull Let f(x) be defined on an interval I
1 We say f(x) is a increasing on I if f(x1) lt f(x2) for all x1 lt x22 We say f(x) is a decreasing on I if f(x1) gt f(x2) for all x1 lt x2
bull Assume f prime(x) exists for all x isin I
1 If f prime(x) gt 0 for all x isin I then f(x) is a increasing on I2 If f prime(x) lt 0 for all x isin I then f(x) is a decreasing on I
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
Lecture Notes for Math 1000 First Previous Next Last 86
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Relative extrema points of inflection and derivative tests
bull Assume f primeprime(x) exists for all x isin I
1 We say f(x) is a concave up if f primeprime(x) gt 0 for all x isin I2 We say f(x) is a concave down if f primeprime(x) lt 0 for all x isin I3 If f primeprime(x) changes sign at x = c we say x = c is a point of inflection
bull (First Derivative Test for Critical Points) Let f(x) be defined near x = cAssume f prime(x) exists for all x near c but not necessarily at c itself
1 If f prime(x) changes from + to minus at x = c then f(c) is a relative maximum2 If f prime(x) changes from minus to + at x = c then f(c) is a relative minimum
bull (Second Derivative Test for Critical Points) Assume f prime(c) = 0
1 If f primeprime(c) lt 0 then f(c) is a relative maximum2 If f primeprime(c) gt 0 then f(c) is a relative minimum
bull If f(c) is a relative extremum (maximum or minimum) then x = c is a criticalpoint namely either f prime(c) does not exist or f prime(c) = 0
Lecture Notes for Math 1000 First Previous Next Last 87
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
Curve sketching
Step 1 Find the xminus and yminus intercepts
Step 2 Find the horizontal and vertical asymptotes
Step 3 Determine the intervals on which the function is increasing or decreasingand classify the relative extrema
Step 4 Determine the intervals on which the function is concave up or concavedown and identify the points of inflection
Step 5 Sketch the curve
Lecture Notes for Math 1000 First Previous Next Last 88
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89
LrsquoHopitalrsquos rule
bull Assume f prime(x) and gprime(x) exist for all x near a and gprime(x) 6= 0 for x near but notequal to a If f(a) = g(a) = 0 then
limxrarra
f(x)
g(x)= lim
xrarra
f prime(x)
gprime(x)
provided that the limit on the right exists
bull If limxrarra
f(x) = plusmninfin and limxrarra
g(x) = plusmninfin then LrsquoHopitalrsquos rule also applies
Furthermore the limits may be taken as one-sided limits
bull Assume f prime(x) and gprime(x) exist for large x and gprime(x) 6= 0 for all large x If bothlimxrarrinfin
f(x) and limxrarrinfin
g(x) are zero (or infinity) then
limxrarrinfin
f(x)
g(x)= lim
xrarrinfin
f prime(x)
gprime(x)
provided that the limit on the right exists Similar results hold when xrarr minusinfin
Lecture Notes for Math 1000 First Previous Next Last 89