I have two definite integrals that I want to show are equal:

INT(h(x)exp(-inx)dx) LIMITS: -pi to pi
INT(h(u)exp(inu)du) LIMITS: x+pi to x-pi

Here a change of variables was done, where u = x-y. I've tried to work this out but I feel I'm missing one step along the way.

Thanks in advance for any help.