Can someone please show me how to solve these three integrals, or proivde a link that does. I cant think of a way to solve it right now and I dont have any free time to do so. Thank you! [tex] \int cos(nx)cos(mx)dx [/tex] [tex] \int sin(nx)sin(mx)dx [/tex] [tex] \int sin(nx)cos(mx) dx [/tex] The thing that makes it tricky is the different coefficients of m and n in each trig term, so you cant make them cos^2(x) or sin^2(x) or use trig identities. (at least I cant see how). Anywho, thanks once more. Cyrus.