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Homework Help: Integrating e^-4tsint

  1. Dec 27, 2008 #1
    1. The problem statement, all variables and given/known data

    Integrating -e-4tsint

    2. Relevant equations

    Our tutor suggested we did this by integrating by parts in a cyclic fashion and things would cancel out

    3. The attempt at a solution

    Taking u = sint t; thus u'=cost
    And v'=-e-4t; thus (1/4)e-4t

    [tex]\int-e[/tex]4tsint = (1/4)e-4tsint-[tex]\int[/tex](1/4)e-4tcost

    Taking u=cost thus u'= -sint
    And v'=(1/4)e-4t; thus (-1/16)e-4t

    [tex]\int-e[/tex]4tsint = (1/4)e-4tsint+(1/16)e-4tcost+(1/16)[tex]\int[/tex]e-4tsint

    Nothing appears to cancel!]
  2. jcsd
  3. Dec 27, 2008 #2


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    Science Advisor
    Homework Helper

    Yes it does. You have the integral of e^(-4t)*sin(t) on both sides. Put them both on the same side and solve for it.
  4. Dec 27, 2008 #3


    Not sure what to do now?
  5. Dec 27, 2008 #4




    YAY that what the answer sheet says
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