1. Jul 30, 2009

### qzack96

I really needed some help with these trig substitution problems. Please write the u and du values for each. I'd really really appreciate it !

1) Integrate [e^x/(e^x +1)] dx

2) Integrate [1/(e^2x +1)] dx

3) Integrate [(1+x)/(1+x^2)] dx

Thank you Again !!!

2. Jul 30, 2009

### rock.freak667

I will give you some hints.

d/dx (ex)=ex
d/dx(constant)=0

Can you think of a substitution for the first one?

(am)n= amn

what can you do with the second one now?

For the third, try making two integrals from it.

3. Jul 30, 2009

### n!kofeyn

Hi qzack96. I see that this is your first post. Welcome! When you post problems, especially homework problems, please try and show us what work you have done so far. It doesn't matter whether it is complete or correct. Post what you have tried or maybe what you try after following rock.freak667's hints.