# What is u equal to?

1. Jun 2, 2013

### kevinnn

1. The problem statement, all variables and given/known data
∫(x^7/(1+x^16)dx

2. Relevant equations

3. The attempt at a solution
I feel like it's so simple. I have tried making u equal to 1+x^16 and then trying to find some sort of chain I can use to make the equation work but no luck. When i saw that arctan was in the correct answer I was lost. Any help appreciated.

2. Jun 3, 2013

### kevinnn

Never mind. I just had to look at it for a second more.

3. Jun 3, 2013

### HallsofIvy

And you let $u= x^8$?

4. Jun 3, 2013

Yes.