As the title says, I am trying to find the definite integral of sech(x) with limits of infinity and minus infinity.
I always get 2pi as my solution, but all calculators and integration applets give pi as the answer.
Below is my method so far:
Could someone please tell me where I have gone wrong?
EDIT: there is an error in line 6 of my method, that extra u is just a typo.