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Laplace Transform inversion

  1. Sep 14, 2012 #1
    I'm inverting this:

    Y = s2 + 15s + 17 / [(s+1)(s2 + 13s - 4)]

    I'm using PF expansion,

    A/(s+1) + Bs + C/(s2 + 13s - 4), I however keep on getting wrong answers, seeing how Runge-Kutta and Taylor approximation disagrees with my final equation.

    My final equation is:

    exp(-13/2t)[19/16cosh√(185)/2t + 13√(185)/74sinh√(185)/2t] - 3/16exp(-t) = y, and it's wrong (considering Runge-Kutta and Taylor approximation disagrees with it).

    Obviously, something's wrong. What did I miss? I'm starting to think that the second term is.. well, there's something wrong with it (Bs + C term). I mean, the numerator is a quadratic, therefore it can't be that simple...

    NOTE: This is NOT homework. I did this to merely tickle my head. The original differential equation is y"+13y'-4y = 3exp(-t), y(0) = y'(0) = 1.
  2. jcsd
  3. Sep 14, 2012 #2
    And apparently according to this site, my inverse is:

    http://wims.unice.fr/wims/wims.gif?cmd=getins&session=7D0AB1E6C0.3&special_parm=insert-1.gif&modif=1347637563 [Broken]

    Crap, what is that i doing there?
    Last edited by a moderator: May 6, 2017
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