Hey there, First time user of this forum. I have a question regarding an integral i've been stuck on for the past few days. I would really appreciate any eye opener into this problem! How do I find the Fourier coefficients for f(x)=xcos(x), x [-∏,∏] So when calculating the coefficient bn I figure that the equation I'll be working with is (1/∏)∫xcos(x)sin(kx)dx (FROM -∏ to ∏). I keep getting down to 1/2∏∫xsin((k+1)x)dx (FROM -∏ to ∏) + 1/2∏∫xsin((k-1)x)dx (FROM -∏ to ∏) . I some how always get a 0 for b1. What am I doing incorrectly??