integrate sin 2 (3x), where the 2 in the question is a square

Hint: if you think about the identity \cos(2w) = 1 - 2 \sin^2(w), you can rearrange to get \sin^2(w) = \frac 1 2 (1 - \cos(2w)). Now you should be able to integrate after substuituting 3x for w.