Question

Rewrite with only sin x and cos x. sin 3x

Answer 1

look at this image

Answer 2

the way to solution is :
sin(3x)=sin(2x+x)
=sin 2x cos x + cos 2x sin x
=(2sinx cos x) cos x +(1-2sin ^2x)sinx
simplify

Answer 3

Okay thank you, i didn't understand it with the picture you sent, but now i do..