Hi there

I was wondering if anyone would be able to help me with a problem I'm having. I've nearly finished a sum and I know the answer but I just haven't managed to quite get there. Any help would really be appreciated.

The answer but as far as I can figure out becomes but does become when I integrate as I've been trying to get to the answer I've been given but can't as isn't =0 when ??

If anyone could help me with the last step, I'd really appreciate it

Thanks