1. The problem statement, all variables and given/known data I need to prove the equation attached. I also have to describe why the integrals vanish. 2. Relevant equations 3. The attempt at a solution I am not sure how to begin. Our teacher told us this equation is known as the orthogonality condition for sines. I also know that n' is a positive integer. I think if I get help starting this I will be able to proceed.