Algebra and Trigonometry 2e

# Review Exercises

### Review Exercises

##### Solving Trigonometric Equations with Identities

For the following exercises, find all solutions exactly that exist on the interval $[ 0,2π ). [ 0,2π ).$

1 .

$csc 2 t=3 csc 2 t=3$

2 .

$cos 2 x= 1 4 cos 2 x= 1 4$

3 .

$2sinθ=−1 2sinθ=−1$

4 .

$tanxsinx+sin( −x )=0 tanxsinx+sin( −x )=0$

5 .

$9sinω−2=4 sin 2 ω 9sinω−2=4 sin 2 ω$

6 .

$1−2tan(ω)= tan 2 (ω) 1−2tan(ω)= tan 2 (ω)$

For the following exercises, use basic identities to simplify the expression.

7 .

$secxcosx+cosx− 1 secx secxcosx+cosx− 1 secx$

8 .

$sin 3 x+ cos 2 xsinx sin 3 x+ cos 2 xsinx$

For the following exercises, determine if the given identities are equivalent.

9 .

$sin 2 x+ sec 2 x−1= ( 1− cos 2 x )( 1+ cos 2 x ) cos 2 x sin 2 x+ sec 2 x−1= ( 1− cos 2 x )( 1+ cos 2 x ) cos 2 x$

10 .

$tan 3 x csc 2 x cot 2 xcosxsinx=1 tan 3 x csc 2 x cot 2 xcosxsinx=1$

##### Sum and Difference Identities

For the following exercises, find the exact value.

11 .

$tan( 7π 12 ) tan( 7π 12 )$

12 .

$cos( 25π 12 ) cos( 25π 12 )$

13 .

$sin(70°)cos(25°)−cos(70°)sin(25°) sin(70°)cos(25°)−cos(70°)sin(25°)$

14 .

$cos(83°)cos(23°)+sin(83°)sin(23°) cos(83°)cos(23°)+sin(83°)sin(23°)$

For the following exercises, prove the identity.

15 .

$cos( 4x )−cos( 3x )cosx= sin 2 x−4 cos 2 x sin 2 x cos( 4x )−cos( 3x )cosx= sin 2 x−4 cos 2 x sin 2 x$

16 .

$cos(3x)− cos 3 x=−cosx sin 2 x−sinxsin(2x) cos(3x)− cos 3 x=−cosx sin 2 x−sinxsin(2x)$

For the following exercise, simplify the expression.

17 .

$tan( 1 2 x )+tan( 1 8 x ) 1−tan( 1 8 x )tan( 1 2 x ) tan( 1 2 x )+tan( 1 8 x ) 1−tan( 1 8 x )tan( 1 2 x )$

For the following exercises, find the exact value.

18 .

$cos( sin −1 ( 0 )− cos −1 ( 1 2 ) ) cos( sin −1 ( 0 )− cos −1 ( 1 2 ) )$

19 .

$tan( sin −1 ( 0 )+ sin −1 ( 1 2 ) ) tan( sin −1 ( 0 )+ sin −1 ( 1 2 ) )$

##### Double-Angle, Half-Angle, and Reduction Formulas

For the following exercises, find the exact value.

20 .

Find $sin( 2θ ),cos( 2θ ), sin( 2θ ),cos( 2θ ),$ and $tan( 2θ ) tan( 2θ )$ given $cosθ=− 1 3 cosθ=− 1 3$ and $θ θ$ is in the interval $[ π 2 ,π ]. [ π 2 ,π ].$

21 .

Find $sin( 2θ ),cos( 2θ ), sin( 2θ ),cos( 2θ ),$ and $tan( 2θ ) tan( 2θ )$ given $secθ=− 5 3 secθ=− 5 3$ and $θ θ$ is in the interval $[ π 2 ,π ]. [ π 2 ,π ].$

22 .

$sin( 7π 8 ) sin( 7π 8 )$

23 .

$sec( 3π 8 ) sec( 3π 8 )$

For the following exercises, use Figure 1 to find the desired quantities.

Figure 1
24 .

25 .

For the following exercises, prove the identity.

26 .

$2cos( 2x ) sin( 2x ) =cotx−tanx 2cos( 2x ) sin( 2x ) =cotx−tanx$

27 .

$cotxcos(2x)=−sin(2x)+cotx cotxcos(2x)=−sin(2x)+cotx$

For the following exercises, rewrite the expression with no powers.

28 .

$cos 2 x sin 4 (2x) cos 2 x sin 4 (2x)$

29 .

$tan 2 x sin 3 x tan 2 x sin 3 x$

##### Sum-to-Product and Product-to-Sum Formulas

For the following exercises, evaluate the product for the given expression using a sum or difference of two functions. Write the exact answer.

30 .

$cos( π 3 )sin( π 4 ) cos( π 3 )sin( π 4 )$

31 .

$2sin( 2π 3 )sin( 5π 6 ) 2sin( 2π 3 )sin( 5π 6 )$

32 .

$2cos( π 5 )cos( π 3 ) 2cos( π 5 )cos( π 3 )$

For the following exercises, evaluate the sum by using a product formula. Write the exact answer.

33 .

$sin( π 12 )−sin( 7π 12 ) sin( π 12 )−sin( 7π 12 )$

34 .

$cos( 5π 12 )+cos( 7π 12 ) cos( 5π 12 )+cos( 7π 12 )$

For the following exercises, change the functions from a product to a sum or a sum to a product.

35 .

$sin(9x)cos(3x) sin(9x)cos(3x)$

36 .

$cos(7x)cos(12x) cos(7x)cos(12x)$

37 .

$sin(11x)+sin(2x) sin(11x)+sin(2x)$

38 .

$cos(6x)+cos(5x) cos(6x)+cos(5x)$

##### Solving Trigonometric Equations

For the following exercises, find all exact solutions on the interval $[ 0,2π ). [ 0,2π ).$

39 .

$tanx+1=0 tanx+1=0$

40 .

$2sin(2x)+ 2 =0 2sin(2x)+ 2 =0$

For the following exercises, find all exact solutions on the interval $[ 0,2π ). [ 0,2π ).$

41 .

$2 sin 2 x−sinx=0 2 sin 2 x−sinx=0$

42 .

$cos 2 x−cosx−1=0 cos 2 x−cosx−1=0$

43 .

$2 sin 2 x+5sinx+3=0 2 sin 2 x+5sinx+3=0$

44 .

$cosx−5sin( 2x )=0 cosx−5sin( 2x )=0$

45 .

$1 sec 2 x +2+ sin 2 x+4 cos 2 x=0 1 sec 2 x +2+ sin 2 x+4 cos 2 x=0$

For the following exercises, simplify the equation algebraically as much as possible. Then use a calculator to find the solutions on the interval $[0,2π). [0,2π).$ Round to four decimal places.

46 .

$3 cot 2 x+cotx=1 3 cot 2 x+cotx=1$

47 .

$csc 2 x−3cscx−4=0 csc 2 x−3cscx−4=0$

For the following exercises, graph each side of the equation to find the approximate solutions on the interval $[0,2π). [0,2π).$

48 .

$20 cos 2 x+21cosx+1=0 20 cos 2 x+21cosx+1=0$

49 .

$sec 2 x−2secx=15 sec 2 x−2secx=15$