I wrote the integral as .

Then I switched the order of integration and used Weierstrass substitution to get .

Finally I let and got

Sometimes Wolfram Alpha returns which reduces to my solution if is real and positive.

But other times it returns which reduces to if is real and positive. On another forum this was stated as the solution. But this cannot be the solution for when and it's not even the solution for when . Is it the solution for ?

EDIT: It's not the solution for either.