1. The problem statement, all variables and given/known data Well it is not the problem itself that bothers me but the maths behind a part of it. As part of finding the coefficient I had to solve the integral of (Sin(x))^(2l+ 1). The solution given by the solution manual just pretty much jumps to the final answer http://i.imgur.com/hhoeLKE.png 2. Relevant equations ... 3. The attempt at a solution Using substitution and the binomial theorem I was able to get a solution (of the integral part only, It would still need solving for the coefficient) and got this http://i.imgur.com/wnOUNIp.png The problem is I dont see how to get from my answer to the one on the solution manual. I know they are equivalent because I checked numerically for different values of l.