C3 Past Trig Questions 1. (a) Show that tan 2 cos 1 2 sin (2) (b) Hence find, for -180° θ < 180°, all the solutions of 1 2 cos 1 2 sin 2 Give your answers to 1 decimal place. (3) (Total 5 marks) 2. (a) Express 2 sin θ – 1.5 cos θ in the form R sin (θ – α), where R > 0 and 0 < α < . 2 Give the value of α to 4 decimal places. (3) (b) (i) Find the maximum value of 2 sin θ – 1.5 cos θ. (ii) Find the value of θ, for 0 θ < , at which this maximum occurs. (3) Tom models the height of sea water, H metres, on a particular day by the equation , 12 0 , 25 4 cos 5 . 1 25 4 sin 2 6 t t t H where t hours is the number of hours after midday. (c) Calculate the maximum value of H predicted by this model and the value of t, to 2 decimal places, when this maximum occurs.
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C3 Past Trig Questions
1. (a) Show that
tan2cos1
2sin
(2)
(b) Hence find, for -180° θ < 180°, all the solutions of
12cos1
2sin2
Give your answers to 1 decimal place.(3)
(Total 5 marks)
2. (a) Express 2 sin θ – 1.5 cos θ in the form R sin (θ – α), where R > 0 and 0 < α < .2
Give the value of α to 4 decimal places.(3)
(b) (i) Find the maximum value of 2 sin θ – 1.5 cos θ.
(ii) Find the value of θ, for 0 θ < , at which this maximum occurs.(3)
Tom models the height of sea water, H metres, on a particular day by the equation
,120,25
4cos5.125
4sin26
tttH
where t hours is the number of hours after midday.
(c) Calculate the maximum value of H predicted by this model and the value of t, to 2 decimal places, when this maximum occurs.
(3)
(d) Calculate, to the nearest minute, the times when the height of sea water is predicted, by this model, to be 7 metres.
(6)(Total 15 marks)
3. (a) Express 5 cos x – 3 sin x in the form R cos(x + α), where R > 0 and 0 < α < .21
(4)
(b) Hence, or otherwise, solve the equation
5 cos x – 3 sin x = 4
for 0 x < 2 ,giving your answers to 2 decimal places.(5)
(Total 9 marks)
4. Solve
cosec2 2x – cot 2x = 1
for 0 x 180°.(Total 7 marks)
5. (a) Use the identity cos2 θ + sin2 θ = 1 to prove that tan2 θ = sec2 θ – 1.(2)
(b) Solve, for 0 ≤ θ < 360°, the equation
2 tan2 θ + 4 sec θ + sec2 θ = 2(6)
(Total 8 marks)
6. (a) Use the identity cos(A + B) = cosA cosB – sinA sinB, to show that
cos 2A = 1 – 2sin2A(2)
The curves C1 and C2 have equations
C1: y = 3sin 2x
C2: y = 4 sin2x – 2cos 2x
(b) Show that the x-coordinates of the points where C1 and C2 intersect satisfy the equation
4cos 2x + 3sin 2x = 2(3)
(c) Express 4cos2x + 3sin 2x in the form R cos(2x – α), where R > 0 and 0 < α < 90°, giving the value of α to 2 decimal places.
(3)
(d) Hence find, for 0 ≤ x < 180°, all the solutions of
4cos 2x + 3sin 2x = 2
giving your answers to 1 decimal place.(4)
(Total 12 marks)
7. (a) Write down sin 2x in terms of sin x and cos x.(1)
(b) Find, for 0 < x < π, all the solutions of the equation
cosec x – 8 cos x = 0
giving your answers to 2 decimal places.(5)
(Total 6 marks)
8. (a) (i) By writing 3θ = (2θ + θ), show that
sin 3θ = 3 sinθ – 4 sin3θ.(4)
(ii) Hence, or otherwise, for ,3
0 solve
8 sin3θ – 6 sin θ + 1 = 0.
Give your answers in terms of π.(5)
(b) Using ,sincoscossin)sin( or otherwise, show that
).26(4115sin
(4)(Total 13 marks)
9. (a) Express 3 cos θ + 4 sin θ in the form R cos(θ – α), where R and α are constants, R > 0 and 0 < α < 90°.
(4)
(b) Hence find the maximum value of 3 cos θ + 4 sin θ and the smallest positive value of θ for which this maximum occurs.
(3)
The temperature, f (t), of a warehouse is modelled using the equation
f(t) = 10 + 3 cos(15t)° + 4 sin(15t)°,
where t is the time in hours from midday and 0 t < 24.
(c) Calculate the minimum temperature of the warehouse as given by this model.(2)
(d) Find the value of t when this minimum temperature occurs.(3)
(Total 12 marks)
10. f(x) = 5cosx + 12sinx
Given that f(x) = Rcos(x – α), where R > 0 and 2
0 ,
(a) find the value of R and the value of α to 3 decimal places.(4)
(b) Hence solve the equation
5 cosx + 12sinx = 6
for 0 ≤ x < 2π.(5)
(c) (i) Write down the maximum value of 5cosx + 12sinx.(1)
(ii) Find the smallest positive value of x for which this maximum value occurs.(2)
(Total 12 marks)
11. (a) Given that sin2θ + cos2θ ≡ 1, show that 1 + cot2θ ≡ cosec2θ.(2)
(b) Solve, for 0 ≤ θ < 180°, the equation
2cot2θ – 9cosecθ = 3,
giving your answers to 1 decimal place.(6)
(Total 8 marks)
12. (a) Use the double angle formulae and the identity
cos(A + B) ≡ cosA cosB – sin A sinB
to obtain an expression for cos 3x in terms of powers of cos x only.(4)
(b) (i) Prove that
2)12(,sec2
cossin1
sin1cos
nxxx
xx
x.
(4)
(ii) Hence find, for 0 < x < 2π, all the solutions of
4cos
sin1sin1
cos
xx
xx
.
(3)(Total 11 marks)
13. (a) Express 3 sin x + 2 cos x in the form R sin(x + α) where R > 0 and 0 < α < .2
(4)
(b) Hence find the greatest value of (3 sin x + 2 cos x)4.(2)
(c) Solve, for 0 < x < 2π, the equation
3 sin x + 2 cos x = 1,
giving your answers to 3 decimal places.(5)
(Total 11 marks)
14. (a) Prove that
.90,2cosec2sincos
cossin
n
(4)
(b) On the axes below, sketch the graph of y = 2 cosec 2θ for 0° < θ < 360°.
y
O 9 0 1 8 0 2 7 0 3 6 0
(2)
(c) Solve, for 0° < θ < 360°, the equation
,3sincos
cossin
giving your answers to 1 decimal place.(6)
(Total 12 marks)
15. (a) By writing sin 3θ as sin (2θ + θ), show that
sin 3θ = 3sinθ – 4sin3θ.(5)
(b) Given that sinθ = 43 , find the exact value of sin 3θ.
(2)(Total 7 marks)
16.
The diagram above shows an oscilloscope screen.
The curve shown on the screen satisfies the equation
.sincos3 xxy
(a) Express the equation of the curve in the form y = Rsin(x + α), where R and α are constants, R > 0
and 0 < α < .2
(4)
(b) Find the values of x, 0 ≤ x < 2, for which y = 1.(4)
(Total 8 marks)
17. (i) Prove that
sec2x – cosec2 x ≡ tan2x – cot2x.(3)
(ii) Given that
y = arccos x, –1 ≤ x ≤ 1, and 0 ≤ y ≤ π
(a) express arcsin x in terms of y.(2)
(b) Hence evaluate arccos x + arcsin x. Give your answer in terms of π.(1)
(Total 6 marks)
18. (a) Using sin2θ + cos2θ ≡ 1, show that cosec2θ – cot2 θ ≡ 1.(2)
(b) Hence, or otherwise, prove that
cosec4θ – cot4θ ≡ cosec2θ + cot2θ.(2)
(c) Solve, for 90° < θ < 180°,
cosec4θ – cot4θ = 2 – cot θ.(6)
(Total 10 marks)
19. (a) Given that cos 43
A , where 270° < A < 360°, find the exact value of sin 2A.
(5)
(b) (i) Show that xxx 2cos3
2cos3
2cos
(3)
Given that
32cos
32cossin3 2 xxxy ,
(ii) show that xxy 2sin
dd
(4)(Total 12 marks)
20. (a) Show that
(i) ,)(,sincossincos
2cos41
nxxx
xxx
n
(2)
(ii) 212
21 sincoscos)2sin2(cos xxxxx
(3)
(b) Hence, or otherwise, show that the equation
21
sincos2coscos
can be written as
sin 2θ = cos 2θ.(3)
(c) Solve, for 0 θ 2π,
sin 2θ = cos 2θ,
giving your answers in terms of π.(4)
(Total 12 marks)
21. (a) Differentiate with respect to x
(i) x2e3x+2,(4)
(ii) .3
)2cos( 3
xx
(4)
(b) Given that x = 4 sin(2y + 6), find xy
dd
in terms of x.
(5)(Total 13 marks)
22. f(x) = 12 cos x – 4 sin x.
Given that f(x) = R cos(x + α), where R 0 and 0 α 90°,
(a) find the value of R and the value of α.(4)
(b) Hence solve the equation
12 cos x – 4 sin x = 7
for 0 x 360°, giving your answers to one decimal place.(5)
(c) (i) Write down the minimum value of 12 cos x – 4 sin x.(1)
(ii) Find, to 2 decimal places, the smallest positive value of x for which this minimum value occurs.
(2)(Total 12 marks)
23. (a) Given that 2 sin( + 30) = cos( + 60), find the exact value of tan .(5)
(b) (i) Using the identity cos (A + B) cos A cos B – sin A sin B, prove that
cos 2A 1 – 2 sin2 A.(2)
(ii) Hence solve, for 0 x < 2,
cos 2x = sin x,
giving your answers in terms of .(5)
(iii) Show that sin 2y tan y + cos 2y 1, for 0 y < 21 .
(3)(Total 15 marks)
24. (a) Given that sin2 + cos2 1, show that 1 + tan2 sec2.(2)
(b) Solve, for 0 < 360, the equation
2 tan2 + sec = 1,
giving your answers to 1 decimal place.(6)
(Total 8 marks)
25. (a) Using the identity cos(A + B) cosA cosB – sinA sinB, prove that
cos 2A 1 – 2 sin2 A.(2)
(b) Show that
2 sin 2 – 3 cos 2 – 3 sin + 3 sin (4 cos + 6 sin – 3).(4)
(c) Express 4 cos + 6 sin in the form R sin( + ), where R > 0 and 0 < < 21 .
(4)
(d) Hence, for 0 < , solve
2 sin 2 = 3(cos 2 + sin – 1),
giving your answers in radians to 3 significant figures, where appropriate.(5)
(Total 15 marks)
26.
B G F C
ED
A
2 2 c m
2 cm2 c m
2 c m
This diagram shows an isosceles triangle ABC with AB = AC = 4 cm and BAC = 2 .
The mid-points of AB and AC are D and E respectively. Rectangle DEFG is drawn, with F and G on BC. The perimeter of rectangle DEFG is P cm.
(a) Show that DE = 4 sin .(2)
(b) Show that P = 8 sin + 4 cos.(2)
(c) Express P in the form R sin( + ), where R > 0 and 0 < < 2
.
(4)
Given that P = 8.5,
(d) find, to 3 significant figures, the possible values of .(5)
(Total 13 marks)
27. (a) Sketch, on the same axes, in the interval 0 x 180, the graphs of
y = tan x° and y = 2 cos x°,
showing clearly the coordinates of the points at which the graphs meet the axes.(4)
(b) Show that tan x° = 2 cos x° can be written as
2 sin2 x° + sin x° – 2 = 0.(3)
(c) Hence find the values of x, in the interval 0 x 180, for which tan x° = 2 cos x°.(4)
(Total 11 marks)
28. (i) Given that sin x = 53
, use an appropriate double angle formula to find the exact value of sec 2x.
(4)
(ii) Prove that
cot 2x + cosec 2x cot x, (x 2n
, n ).
(4)(Total 8 marks)
29. (i) (a) Express (12 cos – 5 sin ) in the form R cos ( + ), where R > 0 and0 < < 90°.
(4)
(b) Hence solve the equation
12 cos – 5 sin = 4,
for 0 < < 90°, giving your answer to 1 decimal place.(3)
(ii) Solve
8 cot – 3 tan = 2,
for 0 < < 90°, giving your answer to 1 decimal place.(5)
(Total 12 marks)
30. (a) Prove that
.2costan1tan1
2
2
(4)
(b) Hence, or otherwise, prove
tan2 8
= 3 – 22.
(5)(Total 9 marks)
31. (i) Given that cos(x + 30) = 3 cos(x – 30), prove that tan x = 23 .
(5)
(ii) (a) Prove that
2sin2cos1
tan .
(3)
(b) Verify that = 180 is a solution of the equation sin 2 = 2 – 2 cos 2. (1)
(c) Using the result in part (a), or otherwise, find the other two solutions, 0 < < 360, of the equation sin 2 = 2 – 2 cos 2.
(4)(Total 13 marks)
32. (a) Express sin x + 3 cos x in the form R sin (x + ), where R > 0 and 0 < < 90.(4)
(b) Show that the equation sec x + 3 cosec x = 4 can be written in the form
sin x + 3 cos x = 2 sin 2x.(3)
(c) Deduce from parts (a) and (b) that sec x + 3 cosec x = 4 can be written in the form
sin 2x – sin (x + 60) = 0.(1)
(d) Hence, using the identity sin X – sin Y = 2 cos 2
sin2
YXYX , or otherwise, find the values
of x in the interval 0 x 180, for which sec x + 3 cosec x = 4.(5)
(Total 13 marks)
33. On separate diagrams, sketch the curves with equations
(a) y = arcsin x, 1 x 1,
(b) y = sec x, 3
x 3
, stating the coordinates of the end points
of your curves in each case.(4)
Use the trapezium rule with five equally spaced ordinates to estimate the area of the region
bounded by the curve with equation y = sec x, the x-axis and the lines x = 3
and x = 3
, giving
your answer to two decimal places.(4)
(Total 8 marks)
34. (a) Prove that for all values of x,
sin x + sin (60 x) sin (60 + x).(4)
(b) Given that sin 84 sin 36 = sin , deduce the exact value of the acute angle .(2)
(c) Solve the equation
4 sin 2x + sin (60 2x) = sin (60° + 2x) – 1
for values of x in the interval 0 x < 360, giving your answers to one decimal place.(5)
(Total 11 marks)
35. Find, giving your answers to two decimal places, the values of w, x, y and z for which
(a) ew = 4,(2)
(b) arctan x = 1,(2)
(c) ln (y + 1) – ln y = 0.85(4)
(d) cos z + sin z = 31 , < z < .
(5)(Total 13 marks)
36. (a) Using the formulae
sin (A B) = sin A cos B cos A sin B,cos (A B) = cos A cos B sin A sin B,
show that
(i) sin (A + B) – sin (A – B) = 2 cos A sin B,(2)
(ii) cos (A – B) – cos (A + B) = 2 sin A sin B.(2)
(b) Use the above results to show that
)cos()cos()sin()sin(
BABABABA
= cot A.
(3)
Using the result of part (b) and the exact values of sin 60 and cos 60,
(c) find an exact value for cot 75 in its simplest form.(4)
(Total 11 marks)
37. In a particular circuit the current, I amperes, is given by
I = 4 sin – 3 cos , > 0,
where is an angle related to the voltage.
Given that I = R sin ( ), where R > 0 and 0 < 360,
(a) find the value of R, and the value of to 1 decimal place.(4)
(b) Hence solve the equation 4 sin – 3 cos = 3 to find the values of between 0 and 360.
(5)
(c) Write down the greatest value for I. (1)
(d) Find the value of between 0 and 360 at which the greatest value of I occurs.(2)
(Total 12 marks)
38. (a) 2
2sin cos1 2 cos 1
M1
2 sin cos 2 cos cos
tan (as required) AG A1 cso 2
Note
M1: Uses both a correct identity for sin 2θ and a correct identityfor cos2θ .Also allow a candidate writing 1+cos2θ =2cos2 θ on the denominator.Also note that angles must be consistent in when candidates applythese identities.A1: Correct proof. No errors seen.
Special Case: For candidate solving, tanθ = k, where, k 21 , to give
θ1 and θ2 = – 180° + θ1, then award M0A0B1 in part (b).Special Case: Note that those candidates who writes tanθ = 1, andgives ONLY two answers of 45° and –135° that are inside the rangewill be awarded SC M0A0B1.
[5]
39. (a) 6.25 or 2.5R B1
1.5 32 4tan awrt 0.6435 M1 A1 3
Note
B1: R = 2.5 or R = 6.25 . For R = ± 2.5, award B0.M1: tan α = ± 2
5.1 or tan α = ± 5.12
A1: α = awrt 0.6435
(b) (i) Max Value 2.5 B1ft
(ii) sin 0.6435 1 or 2their ;awrt 2.21 M1; A1ft 3
Note
B1 : 2.5 or follow through the value of R in part (a).M1: For sin (θ – their α) = 1A1 : awrt 2.21 or 2
+ their α rounding correctly to 3 sf.
(c) Max 8.5 (m)H B1ft4sin 0.6435 125
t
or 4 their (b) answer25
t ;
awrt 4.41t M1; A1 3
Note
B1 : 8.5 or 6 + their R found in part (a) as long as the answer isgreater than 6.
M1: sin
theirt
254
= 1 or 254 t
= their (b) answer
A1: For sin–1 (0.4) This can be implied by awrt 4.41 or awrt 4.40.
(d)46 2.5sin 0.6435 725
t
;
4 1sin 0.6435 0.425 2.5
t
M1; M1
14 0.6435 sin (0.4)25
t
or awrt 0.41 A1
Either awrt 2.1 or awrt 6.7t A1
So, 4 0.6435 0.411517... or 2.730076...25
ct
ddM1
Times 14 : 06, 18 : 43 A1 6
Note
M1: 6 + (their R) sin
theirt
254
= 7, M1:
theirt
254
= Rtheir1
A1: For sin–1 (0.4). This can be implied by awrt 0.41 or awrt 2.73 or othervalues for different α ‘s. Note this mark can be implied by seeing 1.055.A1: Either t = awrt 2.1 or t = awrt 6.7ddM1: either π – their PVc. Note that this mark is dependent upon thetwo M marks.This mark will usually be awarded for seeing either 2.730… or 3.373…A1: Both t = 14 : 06 and t = 18 : 43 or both 126 (min) and 403 (min) orboth 2 hr 6 min and 6 hr 43 min.
[15]
40. (a) 5cosx – 3sin x = R cos(x + α), R > 0, 0 < x< 2
5cosx – 3sinx = Rcos x cos α – R sin x sin α
Equate cos x: 5 = R cos α
Equate sin x: 3 = R sin α
...83095.534;35 22 R R2 = 52 + 32 M1;
34 or awrt 5.8 A1
tan α = c...5404195003.053 tan α = ortanor 3
553
sin α = ortheir 3
R
cos α = ortheir 5
R M1
α = awrt 0.54 or α = awrt 0.17π or
or 5.8awrt A1 4
Hence, 5cos x – 3sin x = 5404.0cos34 x
(b) 5cos x – 3sin x = 4
45405.0cos34 x
cos(x + 0.5404) =
...68599.0344
cos(xtheir α) = Rtheir4
M1
(x + 0.5404) = 0.814826916...c For applying cos–1
Rtheir
4M1
x = 0.2744...c awrt 0.27c A1
(x + 0.5404) = 2π – 0.814826916...c
{ = 5.468358...c} 2π – their 0.8148 ddM1
x = 4.9279...c awrt 4.93c A1 5
Hence, x = {0.27, 4.93}
Note
If there are any EXTRA solutions inside the range 0 ≤ x < 2π,then withhold the final accuracy mark if the candidate wouldotherwise score all 5 marks. Also ignore EXTRA solutionsoutside the range 0 ≤ x < 2π .
[9]
41. cosec2 2x – cot 2x = 1, (eqn *)0 ≤ x ≤180°
Using cosec2 2x = 1 + cot22x gives Writing down or usingcosec22x = ±1 ± cot22x M1
1 + cot2 2x – cot 2x = 1 or cosec2θ = ±1 ± cot2θ
cot 2 2 x – cot 2 x = 0 orcot2 2x = cot 2x For either cot 2 2 x – cot 2 x {=0}
or cot2 2x = cot 2x A1
cot 2x(cot 2x–1)= 0 orcot 2x = 1 Attempt to factorise or solve a
quadratic (See rules forfactorising quadratics) or
cancelling out cot 2x from bothsides. dM1
cot 2x = 0 or cot 2x = 1 Both cot 2x = 0 and cot 2x = 1. A1
cot 2x = 0 (tan 2x→ ∞) 2x = 90, 270
Candidate attempts to divide at leastone of their principal anglesby 2.
This will be usually implied byseeingx = 22.5 resulting from
cot 2x = 1.
ddM1
x = 45, 135
cot 2x = 1 tan 2x = 1 2x = 45,225 x = 22.5, 112.5
Overall, x = {22.5, 45, 112.5, 135} Both x = 22.5 and x = 112.5 A1
Both x = 45 and x = 135 B1
If there are any EXTRA solutions inside the range 0 ≤ x ≤180°and the candidate would otherwise score FULL MARKS thenwithhold the final accuracy mark (the sixth mark in this question).
Also ignore EXTRA solutions outside the range 0 ≤ x ≤180° .[7]
49. (a) cos (2x + x) = cos 2x cos x – sin 2x sin x M1= (2 cos2 x – 1) cos x – (2 sin x cos x) sin x M1= (2 cos2 x – 1) cos x – 2(1 – cos2 x) cos x any correct expression A1= 4cos3 x – 3cosx A1 4
(b) (i)xxxx
xx
xx
cos)sin1()sin1(cos
cossin1
sin1cos 22
M1
xxxxx
cos)sin1(sinsin21cos 22
A1
xxx
cos)sin1()sin1(2
M1
(*)sec2cos
2 xx cso A1 4
(c) sec x = 2 or cos x = 21
M1
x = 3
5,3
accept awrt 1.05, 5.24 A1, A1 3
[11]
50. (a) Complete method for R: e.g. R cos = 3, R sin = 2, R = )23( 22 M1
R = 13 or 3.61 (or more accurate) A1
Complete method for tan = 32
[Allow tan = 23
] M1
= 0.588 (Allow 33.7°) A1 4
1st M1 for correct method for R2nd M1 for correct method for tanNo working at all: M1A1 for 13, M1A1 for 0.588 or 33.7°.N.B. R cos = 2, R sin = 3 used, can still score M1A1 for R,
but loses the A mark for .cos = 3, sin = 2: apply the same marking.
Must be – their 0.281 or 180° – their 16.1°or (x + 0.588) = 2 + 0.28103... M1
Must be 2 + their 0.281 or 360° + their 16.1°x = 2.273 or x = 5.976 (awrt) Both (radian only) A1 5If 0.281 or 16.1° not seen, correct answers imply this A mark
Alt (i) Squaring to form quadratic in sin x or cos x M1[13 cos2x – 4cosx – 8 = 0, 13 sin2x – 6sinx – 3 = 0]Correct values for cos x = 0.953.... –0.646;or sinx = 0.767, 2.27 awrt A1For any one value of cos x or sin x, correct method fortwo values of x M1x = 2.273 or x = 5.976 (awrt) Both seen anywhere A1Checking other values (0.307, 4.011 or 0.869, 3.449)and discarding M1
Alt (ii) Squaring and forming equation of form a cos2x + bsin2x = c9sin2x + 4cos2x + 12sin2x = 1 12sin2x + 5cos2x = 11Setting up to solve using R formula e.g. 13cos(2x – 1.176) = 11 M1
...0(562.013
11cos)176.12( 1
x () A1
(2x – 1.176) = 2 – , 2 + ,................ M1x = 2.273 or x = 5.976 (awrt) Both seen anywhere A1Checking other values and discarding M1
[11]
51. (a)
sincoscossin
sincos
cossin 22
M1
M1 Use of common denominator to obtain single fraction
= sincos
1M1
M1 Use of appropriate trig identity (in this case sin2 + cos2 = 1)
= 2sin21
1Use of sin 2 = 2sin cos M1
= 2cosec2 (*) A1cso 4
Alt. (a)
tan1tan
tan1tan
sincos
cossin 2
M1
= tan
sec 2
M1
= 2sin21
1sincos
1
M1
= 2cosec2 (*) (cso) A1If show two expressions are equal, need conclusion such as QED, tick true.
(b)y
2
– 2
O 9 0º 1 8 0 º 2 7 0 º 3 6 0 º
Shape (May be translated but need to see 4 “sections”) B1
T.P.s at y = 2, asymptotic at correct x-values(dotted lines not required) B1dep 2
(c) 2cosec2 = 3
sin2 = 32
Allow 32sin
2
[M1 for equation in sin2] M1, A1
(2) = [41.810...°, 138.189...°; 401.810...°, 498.189...°] M1; M11st M1 for , 180 – ; 2nd M1 adding 360° to at least one of values M1; M1 = 20.9°, 69.1°, 200.9°, 249.1° (1 d.p.) awrt
1st A1for any two correct, 2nd A1 for other two A1, A1 6Extra solutions in range lose final A1 onlySC: Final 4 marks: = 20.9°, after M0M0 is B1; record as M0M0A1A0
Alt. (c) 3tan
1tan
and form quadratic, tan2 – 3tan + 1 = 0 M1, A1
(M1 for attempt to multiply through by tan,A1 for correct equation above).
Solving quadratic 2
53[tan = 2.618... or = 0.3819...] M1
= 69.1°, 249.1° = 20.9°, 200.9° (1 d.p.) M1, A1, A1(M1 is for one use of 180° + °, A1A1 as for main scheme)
[12]
52. (a) sin 3 = sin (2 + ) = sin 2 cos + cos 2 sin B1= 2 sin cos2 + (1 – 2 sin2 ) sin B1B1= 2sin – 2 sin3 + sin – 2 sin3 M1= 3 sin – 4 sin3 * cso A1 5
(b)16
3916
334
33434
4333sin
3
or exact M1A1 2
equivalent[7]
53. (a) R2 = (3)2 +12 R = 2 M1A1
tan = 3 = 3
accept awrt 1.05 M1 A1 4
(b) sin(x + their ) = 21
M1
x + their =
613,
65
6
A1
xi = 6
11,2
accept awrt 1.57, 5.76 M1 A1 4
The use of degrees loses only one mark in this question.Penalise the first time it occurs in an answer and then ignore.
[8]
54. (i) sec2 x – cosec2 x = (1 + tan2 x) – (1 + cot2 x) M1 A1= tan2 x – cot2 x * cso A1 3
and multiplying both sides by cos x. (sinx = 2cos2x) M1
Using sin2 x + cos2 x = 1 M12 sin2 x + sin x – 2 = 0 (*) A1 3
(c) Solving quadratic: sin x = 4
171 (or equiv.) M1 A1
x = 51.3 (3 s.f. or better, 51.33…) A1x = 128.7 (accept 129) (3 s.f. or better) 180 – ( 90n) B1ft 4
[11]
65. (i) A correct form of cos 2x used M1
1 – 22
53
or
22
53
54
or 1
542
2
257
A1
xx
2cos12sec ; =
7
25 or
743 M1A1 4
(ii) (a) xx
x2sin
12sin2cos
or (b) xx 2sin
12tan
1 M1
Forming single fraction (or ** multiplying both sides by sin2x) M1Use of correct trig. formulae throughout and producing expressionin terms of sinx and cosx M1