Question

if x+6=3sin(theta) for 0 12 years ago

Answer 1

i replace theta by k for ease
sin(k)=(x+6)/3
use the relation cos(2k)=cos^2(k)-sin^2(k)=1-2sin^2(k)

Answer 2

it says that's incorrect
no idea how
If x + 6 = 3 \sin(\theta) for 0 < \theta < \pi/2 express \cos(2\theta) in terms of x.
that's the full question