# Thread: Double angle question help

1. ## Double angle question help

The angle x lies in the interval pi/2 lessthanequal x lessthanequal pi, and sin^2 x = 8/9. Determine the value of sin 3x

2. Originally Posted by Devi09
The angle x lies in the interval pi/2 lessthanequal x lessthanequal pi, and sin^2 x = 8/9. Determine the value of sin 3x
Note that sin(3x) = sin(2x + x) = sin(2x) cos(x) + sin(x) cos(2x)

What are sin(2x) and cos(2x)?

-Dan