Question

Given tantheta = 4/3 and pi < theta < 3pi/2; find cos2theta

Answer 1

Answer:

d. -7/25

Step-by-step explanation:

π<θ<3π/2  in third quadrant

tanθ = 4/3

sinθ = - 4/5

cosθ = - 3/5

cos 2θ = cos²θ - sin²θ = (- 3/5)² - (- 4/5)² = 9/25 - 16/25 = - 7/25

Answer 2

Answer:

-24/7

Step-by-step explanation:

We know that,  

tan

2

θ

=

2

tan

θ

1

−

tan

2

θ

.

∴

tan

2

θ

=

2

⋅

3

4

1

−

9

16

=

3

2

⋅

16

7

=

24

7

.