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Laplace transform of sin(4t+5)

  1. Sep 16, 2009 #1
    1. The problem statement, all variables and given/known data

    get laplace transform of sin(4t+5)


    2. Relevant equations
    using some trig identity i.e. Sin(a+b)=sin(a)cos(b)+cos(a)sin(b)
    or any other that could simplify it

    3. The attempt at a solution
    applying the trig identity
    =sin(4t)cos(5)+cos(4t)sin(5)
    taking the transform :
    [tex] 4cos(5)\frac {1}{s^2+16} +s*sin(5)\frac{1}{s^2+16} [/tex]
    why do i not trust this result, can anyone point me in the right direction?
     
    Last edited: Sep 16, 2009
  2. jcsd
  3. Sep 16, 2009 #2

    Dick

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    Why don't you trust it? It looks fine to me.
     
  4. Sep 16, 2009 #3
    It might be right but i would like an alternative method to confirm the answer i got
     
  5. Sep 16, 2009 #4

    Dick

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    You could compute it directly. Integrate sin(4t+5)*exp(-st) from t=0 to t=infinity. You'll get the same thing.
     
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