where the wave equation is Psi_n = sqrt(2/a)sin(n*pi*x/a). When you do the integral of -inf to +inf of x|Psi|^2, the CRC handbook works it out to be: (x^2)/4 - (xsin(2ax))/4a - cos(2ax)/(8a^2). And I know the solution works out to be a/2 somehow but I don't know how to get it. I worked it down to: ax - 2sin(2ax) - 2/ax = 0. I don't know if this is the right track. Can someone shed some light on this? Thanks in advance.