# Homework Help: Integration problem

1. May 6, 2010

### thereddevils

1. The problem statement, all variables and given/known data

evaluate $$\int \frac{1}{x^2+1} dx$$

2. Relevant equations

3. The attempt at a solution

This cant be $$\frac{\ln x^2+1}{2x}$$ , my first thought on this .

Then , i tried partial fraction , it didn't work either .

2. May 6, 2010

### Staff: Mentor

Re: integration

Your first thought led you to try an ordinary substitution, u = x^2 + 1. This won't work, though, because du = 2xdx, so there's no way to change the given integrand to du/u.

If you know a derivative formula for which d/dx(something) = 1/(x^2 + 1) then that will be helpful in this problem. If you don't know or don't remember such a formula, a trig substitution will be the way to go, with tan u = x/1.