Integral using parseval (supposed to be simple )

[jjongmu]

integral using parseval (supposed to be simple :( )

Hi everyone. I am stuck in one of the assignment problems, and I think it's supposed to be simple, but it's just that I don't see how it worked out.

I have to take integral(1/a^2+w^2)dw, from -a to a.
I know the answer but I have no single clue how it came out.
It would be great if someone could explain with steps :(
Thank you and have a great day.

 

[trambolin]

Do you mean this?
\int \frac{1}{a^2+w^2}dw = \frac{1}{a}\tan^{-1}\frac{w}{a}+c

or this?

\int \left(\frac{1}{a^2}+{w^2}\right)dw = \ldots

Why Parseval?