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Homework Help: Having trouble finding the Integral

  1. Oct 6, 2006 #1

    I am having trouble getting started with this integral.

    [itex]\int sin2x ln(cos2x) dx[/itex]

    My first thought goes to using integration by parts to solve this but I am still getting stuck. I also know that [itex]sin2x = 2sinxcosx[/itex] but again I'm not seeing how that would help me so I'm back to integration by parts.

    My issue is if I set [itex]u = ln(cos2x)[/itex] then I'm having trouble figuring out what [itex]du[/itex] is. I know it's just finding the derivative but I can't for the life of me remember how to do that. Then if I set [itex]dv = sin2x dx[/itex] then [itex]v = - \frac{1}{2} cos2x[/itex]

    Any help or suggestions would be greatly appreciated.
  2. jcsd
  3. Oct 6, 2006 #2


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    Set u=cos(2x).
  4. Oct 6, 2006 #3
    Oh my gosh...I was making that WAY harder then it needed to be. Thank you very much arildno.
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