Alright, so here's my problem. I've got a wavefunction between -L/2 and L/2 (symmetric around 0). It's a square wave and it is in an infinite potential well. That's all I know about it. I need to find the wavefunction of it. I was thinking of doing a Fourier sine/cosine series but I'm stuck. Here's what I've tried: [itex] f(x) = \Theta (x+L/2) \sqrt(2/L) cos(n\pi*x/L) [itex] The thought process here was that I needed an f(x) to put into the Fourier series (I'm just going off the wikipedia definition). I have the step function in there because there is only one wave so before -L/2 the wavefunction is 0. But that is what's tripping me up - I don't know how to take the integral of a step function to get my Fourier coefficients. Maybe I don't need that step function. Maybe I don't even need to do a Fourier series. I guess at this point I'm confused and frustrated and need a push in the right direction. Any suggestions would be greatly appreciated! Thanks in advance!