# Double integral and reversing order

1. Feb 14, 2012

### Nope

1. The problem statement, all variables and given/known data
http://img10.imageshack.us/img10/3390/55486934.jpg [Broken]

2. Relevant equations
This is what I was thinking: tan−1(∏x)−tan−1(x)=∫$^{g(x)}_{f(x)}$h(y)dy

3. The attempt at a solution
I don't really understand how to do this question

Last edited by a moderator: May 5, 2017
2. Feb 14, 2012

### Dick

Big hint. You can write the numerator as
$$\int_x^{\pi x} \frac{1}{1+t^2} dt$$
Now follow the rest of the problem suggestion.

3. Feb 14, 2012

### Nope

Thanks for the hint!