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Homework Help: Using Laplace Transform to solve a differential equation

  1. Nov 18, 2012 #1
    1. The problem statement, all variables and given/known data

    y" + y = 4δ(t-2π); y(0)=1, y'(0)=0

    2. Relevant equations

    L[f(t-a) U(t-a)] = [itex]e^{-as}[/itex] L[f(t)]

    L[δ(t-c)] = [itex]e^{-cs}[/itex]

    3. The attempt at a solution

    My answer is: cos(t) + 4U(t-2π)sin(t-2π).

    When I used Wolframalpha it gave me 4sin(t)U(t-2π) + cos(t)
  2. jcsd
  3. Nov 18, 2012 #2

    I like Serena

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    Homework Helper

    Hi november1992!

    So what is your question?

    Did you know that sin(t-2π)=sin(t) since the sine has a period of 2π?
  4. Nov 18, 2012 #3
    I meant to ask why is my answer different. I don't remember any of the trig identities so I'll have to review them.

    Thanks for answering my question!
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