# Indefinite integral

menco

## Homework Statement

(e^-x)/(1+e^-x)dx

## Homework Equations

Integral of e^x function

## The Attempt at a Solution

I am completely lost with the problem, the fact that it is e^-x and not e^x has me stupped as well as the division.

## Answers and Replies

foxjwill
Try $u$-substitution.

menco
so if I let u=1+e^-x?

Dickfore
yes?

foxjwill
so if I let u=1+e^-x?

Well, does it work?

menco
I still cant figure it out so I gave up and will try again later

foxjwill
I still cant figure it out so I gave up and will try again later

When you do get back to it, answer this: What is $du$ when $u=1+e^{-x}$?

menco
Will du = -e^-x dx