13.4 Limits of Infinite Sequences Objective To find or estimate the limit of an infinite sequence or to determine that the limit does not exist. • Sequences with a numerical limit • Sequences with no limit • Sequences with a limit of infinity
13.4 Limits of Infinite Sequences
Objective
To find or estimate the limit of an infinite sequence
or to determine that the limit does not exist.
• Sequences with a numerical limit
• Sequences with no limit
• Sequences with a limit of infinity
Limits
Limits are written in the form below.
It is read “The limit of 1 over n as n
approaches infinity”. 1limn n
Limits are used to determine how a function,
sequence, or series will behave as the
independent variable approaches a certain
value, often infinity.
A graph of the sequence 1
𝑛for 𝑛 = 1,2,3,… , 10
1limn n
The terms are 1
1,1
2,1
3, … ,
1
10
= 0
2,4,8,16,32,…… . . lim𝑛→∞2𝑛 = ∞
13.4 Limits of Infinite Sequences
−1,1,−1,1,−1…… . .
lim𝑛→∞
−5𝑛 =−∞
−5,−10,−15,−20,…… . .
lim𝑛→∞
(−1)𝑛 = 𝐷𝑁𝐸 (does not exist)
13.4 Limits of Infinite Sequences
Situations in Which a Sequence Has No Limit
If the terms of a sequence do not " "
on a single value, we say that the limit of the
sequence
home in
DNE.
1
11 2 3 4, , , ,...., ,...
2 3 4 5 1
nn
n
13.4 Limits of Infinite Sequences
1
11 2 3 4, , , ,...., ,...
2 3 4 5 1
nn
n
1
1lim
1
n
n
nDNE
n
13.4 Limits of Infinite Sequences
Infinite Limits
increaseWhen the terms of a sequence or
without decre bouase nd.
3,7,11,15,....,4 1,...n lim 4 1n
n
-10, 100, 1000,...., 10 ,...n lim 10nn
13.4 Limits of Infinite Sequences
11 1 1 11 ,1 ,1 ,1 ,....1 ,...
1 2 3 4
n
n
11 1lim
n
n n
Numerically investigate
13.4 Limits of Infinite Sequences1
limsin .n n
As n gets larger, 1
𝑛gets smaller and smaller.
1
1,1
2,1
3,1
4,1
5,… . .
In fact, 1
𝑛approaches 0. Therefore, lim
𝑛→∞
1
𝑛= 0.
It follows that lim𝑛→∞
𝑠𝑖𝑛1
𝑛=𝑠𝑖𝑛0 = 0
Numerically investigate
13.4 Limits of Infinite Sequences
1limsin .n n
1limsin 0n n
1 1 1 1 1, , , ,.... ,...
2 4 8 16 2
n
10
2lim
n
n
nnt
1/ 21/ 4
1/81/16
1234
Numerically investigate
13.4 Limits of Infinite Sequences
0.99limn
n
Numerically investigate
13.4 Limits of Infinite Sequences
0.99limn
n
Numerically investigate
13.4 Limits of Infinite Sequences
0.99limn
n
Numerically investigate
13.4 Limits of Infinite Sequences
0.99limn
n
0.99 0limn
n
13.4 Limits of Infinite Sequences
If 1, then li
Theo em
m 0
r
n
nr r
0.99limn
n
0
Rational Function Reminders
Rational functions have the form:𝑓(𝑥)
𝑔(𝑥)
where f and g are polynomial functions.
The degree of a polynomial is equal to the
largest exponent in the equation when
written in standard form.
3𝑥4 + 𝑥2 − 1
2𝑥3 − 𝑥2
Guidelines for Finding Limits at ∞
of Rational Functions1. If the degree of the numerator is ___________ the degree
of the denominator, then the limit of the rational function
is _______.
2. If the degree of the numerator is ___________ the degree
of the denominator, then the limit of the rational function
is __.
3. If the degree of the numerator is _______ the degree of
the denominator, then the limit of the rational function is
the __________________ _______________________.
greater than
0
less than
equal to
ratio of the leading coefficients
infinite
4 3
4
3 1lim
2 7nn n
n n
=
1
2
3
3
6lim
3nn n
n
=1
3
Find the limit for each sequence. You can check
by graphing.
lim𝑛→∞
6𝑛5 + 4𝑛3
2𝑛2 − 𝑛 = ∞
=1
2
= 0
= ∞
PracticeEvaluate the following.
3
4 2limn
n
n
2
2
3 2 5lim
4 1
n
n n
n
lim𝑛→∞
1.0001𝑛
lim𝑛→∞
𝑐𝑜𝑠1
𝑛lim𝑛→∞
𝑙𝑜𝑔 𝑐𝑜𝑠1
𝑛
3
40 ∞
1 03
4 2
2 3lim
3x
x x
x x x
0
=2
5
3 2
5 6lim
2 8x
x x
x x
∞8
8 2
6 12 17lim
18 13 24x
x x
x x
1
3lim𝑥→∞
4𝑥3 + 2𝑥2 − 5
𝑥3 + 4
Infinite Series Video
https://www.youtube.com/watch?v=jktaz0ZautY
Homework
Page 496 #1-29
odds