(sigh) I know I've seen how to do this before, but I can't find the notes!
The problem is this:
where a is real.
It is simple enough to show that the integral is equal to a real number, so
as an alternate formula.
Comparing two lines in the book I got this from the integral should be equal to
(For the case a = 0, the integral is simple and comes out to be equal to 2. Obviously I'm not worried about this case.)
Any takers? Thanks in advance.