You're right. I think I know where is my error... Hmm no...
Let me show you what I did : Let , .
So the integral becomes .
Now let .
We know that and that . Furthermore, and .
Therefore we can rewrite the integral as , and from it I reached the result I gave in my first post. I thought I might have made an error for , but I don't think so. Can you help me finding where is my error?
Before I read