1. Integral Problem!

∫dx/(1-e^x)

I have no idea what to set u equal to.

Could someone help me begin this problem?

2. Originally Posted by r2d2
$∫dx/(1-e^x)$
$\int\frac{dx}{1-e^x}=\int\frac{dx}{1-e^x}\cdot\frac{e^{-x}}{e^{-x}}=\int\frac{e^{-x}}{e^{-x}-1}\text{ }dx$...so

3. Ok, So I'm stuck on why you multpilied by $e^(-x)/e^(-x)$

4. Originally Posted by r2d2
Ok, So I'm stuck on why you multpilied by $e^(-x)/e^(-x)$
Let $u=....$. That's why.

5. so setting u=e^(-x), I get the integral of [du/(e^(-x)-1)]-1. Would that be correct?

Then the integral of 1/(u-1)du = ln(u-1)?

6. Originally Posted by r2d2
so setting u=e^(-x), I get the integral of [du/(e^(-x)-1)]-1. Would that be correct?

Then the integral of 1/(u-1)du = ln(u-1)?
You forgot a negative...but

7. great, so i just need to add the negative, and the c, then re-substitute the u function.

Thanks, mate.