I was tutoring an engineer student and we are stuck at this one problem.

Prove that $\displaystyle \frac {1}{T} \int _{0}^{T} [V I \sin ( \theta ) \sin (2 \omega t ) ] dt = 0$

I rarely deal with integrals like this and not really sure how to proceed. He is taking an undergrad. engineering class and I suppose this shouldn't be too difficult. Are there any hints or at least some resource I can read get hints from?

Thank you.