# How to integrate e^x cos(x) using parts?

1. May 31, 2007

### Firepanda

Is it possible to intergrate

e^x (cosx)

i wondered because i tried to intergrate it by parts, but ended up going round in circles.

I wondered because i had this question and im stuck on how to do it :)

http://img505.imageshack.us/img505/320/frfbc8.png

Last edited: Jun 1, 2007
2. Jun 1, 2007

### Dick

Sure it's possible. Just integrate by parts twice. You will get back to where you started - but if you call the integral I, then you will get I=somthing-I. So I=something/2. Not circular. On the other hand the question you posted is done more directly with deMoivre. cos(x)+j*sin(x)=e^(j*x).