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Homework Help: Laplace transformPLEASE HELP

  1. May 24, 2006 #1
    hi,
    i just started doing laplace transform n i have real trouble doing these two questions, anyhelp would be great...

    L{te^t(sint)}
    L^-1{1/((s^2+1)(s-1)^2)}
     
  2. jcsd
  3. May 24, 2006 #2

    J77

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    You need to show some working.

    Starting with the question may help...
     
  4. May 24, 2006 #3
    for the first question t*e^t*sin(t) i got
    (2s-2)/((s-1)^2+1)^2
    and for the L^-1{1/((s^2+1)(s-1)^2)} i got
    (e^s/8)-(s*e^s/4)-(e^-s/8)+(s^2*e^s/4)
    ...doesnt look right does it?
     
  5. May 24, 2006 #4

    LeonhardEuler

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    Gold Member

    The first one is right, let me check the second.
     
  6. May 24, 2006 #5

    LeonhardEuler

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    Gold Member

    Oh, the second is definitely not right. When you take the inverse laplace transform you should get a function of t only with no s. How did you try to do it?
     
  7. May 25, 2006 #6
    oh yea sorry i mean to write t instead of s..my bad~!!
    but after looking at it again i got

    cos(t)/2 - e^t/2 + te^t/2

    i think this one is correct..anyway thanks for all your help :)
     
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