1. The problem statement, all variables and given/known data 2. Relevant equations 3. The attempt at a solution http://i.imgur.com/tktQBsp.jpg I assume that you need to prove that the integral of psi1*psi0 is 0, so I have written out the integral and attempted to solve using integration by parts, but whichever way I write out the integration by parts it doesn't seem to cancel down. Do I need to write the integral as a definite integral instead and evaluate it at limits? Or perhaps invoke some properties of waves instead that will allow me to say =0?