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Standard level

5.06 Trigonometric equations

Worksheet
Graphical solutions
1

Consider the function y = \cos \left(x - 30\right).

a

Sketch the graph of the function for -360 \leq x \leq 360.

b

Sketch the line y = \dfrac{1}{2} on the same number plane.

c

Hence, state all solutions to the equation \cos \left(x - 30\right) = \dfrac{1}{2} over the domain \left( - 360 , 360\right].

2

Consider the function y = \sin \left(x - 60\right).

a

Sketch the graph of the function for -360 \leq x \leq 360..

b

Sketch the line y = \dfrac{1}{2} on the same number plane.

c

Hence, state all solutions to the equation \sin \left(x - 60\right) = \dfrac{1}{2} over the domain \left[ - 360 , 360\right).

3

Consider the function y = 2 \sin 4 x.

a

Sketch the graph of the function for -120\degree \leq x \leq 120\degree.

b

Sketch the line y = 1 on the same number plane.

c

Hence, state all solutions to the equation 2 \sin 4 x = 1 over the domain \left[ - 90 \degree , 90 \degree\right]. Give your answers in degrees.

4

Consider the function y = 2 \sin 2 x.

a

Sketch the graph of the function for -180\degree \leq x \leq 180\degree.

b

State the other function you would add to the graph in order to solve the equation 2 \sin 2 x = 1.

c

Sketch the graph of this function on the same number plane.

d

Hence, state all solutions to the equation 2 \sin 2 x = 1 over the domain \left[ - 180 \degree , 180 \degree\right].

5

Consider the function y = 3 \cos 2 x + 1.

a

Sketch the graph of the function for -180 \leq x \leq 180.

b

State the other function you would add to the graph in order to solve the equation 3 \cos 2 x + 1 = \dfrac{5}{2}.

c

Sketch the graph of this function on the same number plane.

d

Hence, state all solutions to the equation 3 \cos 2 x + 1 = \dfrac{5}{2} over the domain \left[ - 180 , 180\right].

6

Consider the function y = 2 \sin 3 x - 3.

a

Sketch the graph of the function for -60 \leq x \leq 60.

b

State the other function you would add to the graph in order to solve the equation 2 \sin 3 x - 3 = - 2.

c

Sketch the graph of this fuction on the same number plane.

d

Hence, state all solutions to the equation 2 \sin 3 x - 3 = - 2 over the domain \left[ - 120 , 120\right].

7

Consider the function y = - 2 \cos 3 x.

a

Sketch the graph of the function for -120\degree \leq x \leq 120\degree.

b

State the other function you would add to the graph in order to solve the equation - 2 \cos 3 x = -1.

c

Sketch the graph of this function on the same number plane.

d

Hence, state all solutions to the equation - 2 \cos 3 x = -1 over the domain \left[ - 120 \degree , 120 \degree\right].

Technology
8

Solve each equation for the given interval. Round your answers to one decimal place.

a
\cos 2 x = 0.9 for 0 \leq x < 360
b
3\sin 2 x = 1.2 for 0 \leq x < 180
c
4\cos\left(\dfrac{x}{3}+2\right) = 1 for 0 \leq x < 720
9

Consider the equation \sin \left(\dfrac{x}{2} + 60 \degree\right) = \cos \left(\dfrac{x}{2} - 60 \degree\right).

a

State the two functions you would graph in order to solve this equation graphically.

b

Sketch the graph of both of these functions using technology.

c

Hence, state all solutions to the equation over the domain \left[ - 360 \degree, 360 \degree\right].

10

Use technology to solve the following functions over the interval [0 \degree, 360 \degree). Give all solutions to the nearest degree.

a
2 \sin 3 x - 4 \sin 2 x = 0
b
2 \sin x + 5 \cos x = 1
c
\cos 3 x + \cos x = \sin x
d
2 \cos 3 x - 3 \cos 2 x = 0
e
\cos \left(\dfrac{x}{2}\right) - 4 \sin 2 x = 0
f
\sin \left(\dfrac{x}{2}\right) = 7 \cos 3 x
g
4 \sin ^{5}\left(x\right) = - \left( \cos x + 1 \right)
h
\cos ^{3}\left(x\right) + \cos x = - 1
11

Use technology to solve the following equations for 0 \leq x \leq 360. Give all solutions to two decimal places.

a
2 \sin x + 5 \cos x = 1
b
3 \sin 2 x + 2 \sin 3 x = 0
c
3\sin(2x)=x+1
d
2 \cos 3 x + 3 \cos 2 x = 0
e
\cos 3 x + \cos x = \sin x
f
\cos \left(\dfrac{x}{2}\right) - 4 \sin 2 x = 0
g
4 \sin ^{5}\left(x\right) = - \left( \cos x + 1 \right)
h
\cos ^{5}\left(x\right) + \cos x = - 1
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