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Homework Help: How to integrate e^x cos(x) using parts?

  1. May 31, 2007 #1
    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 [Broken]
    Last edited by a moderator: May 2, 2017
  2. jcsd
  3. Jun 1, 2007 #2


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    Science Advisor
    Homework Helper

    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).
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