# Evaluating an integral

1. Oct 2, 2007

### ACLerok

1. The problem statement, all variables and given/known data
Evaluate the integral with respect to f of the following function

3. The attempt at a solution

This if for one of my homeworks. I haven't taken a single math course in almost 2 years so I'm kind of rusty. I'm not sure how to evaluate this. I tried moving the 'a' outside the integral but that doesn't help. I believe there is a trig identity I'm supposed to be able to use. Any tips or hints are greatly appreciated.

2. Oct 2, 2007

### HallsofIvy

Staff Emeritus
That is for the form $$\frac{a^2}{a^2+b^2f^2}$$= $$\frac{1}{1+ \left(\frac{bf}{a})^2}$$.
Does it help you to know that the derivative of arctan(x) is $$\frac{1}{x^2+ 1}$$?