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Determine the Laplace transform for the following functions

  1. Nov 30, 2016 #1
    1. The problem statement, all variables and given/known data
    Can someone check my work?
    upload_2016-11-30_1-2-3.png

    2. Relevant equations


    3. The attempt at a solution
    1. ##\frac{1}{s+2}+\frac{1}{s^2+1}##
    2. ##\frac{2}{s}+\frac{3}{s+4}##
    3. ##\frac{s*sin(-2)+cos(-2)}{s^2+1}##
    4. ##\frac{1}{(s+1)^2}##
    5. Don't really know how to do this one...
     
  2. jcsd
  3. Nov 30, 2016 #2

    rude man

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  4. Nov 30, 2016 #3
    f(t-T)u(t-T) = ##e^{-as}F(s)##
    ##F(s)=\frac{s(sin(-2)+cos(-2)}{s^2+1}##
    3. ##\frac{e^{-2s}*s*sin(-2)+cos(-2)}{s^2+1}##

    5. ##(\frac{-5}{3s^2}+\frac{5}{s}) - ((\frac{-5}{3s^2}+\frac{7}{s})*e^{-4.2s})##
     
  5. Nov 30, 2016 #4

    rude man

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    $3 you copied F(s) incorrectly. Correct it first.
    #5 looks OK now but I don't have time right now to be sure.
     
  6. Nov 30, 2016 #5
    upload_2016-11-30_21-18-9.png
    a = 1, b=-2
    What did I do wrong?
    ##F(s)=\frac{s*sin(-2)+cos(-2)}{s^2+1}##
     
  7. Dec 1, 2016 #6

    rude man

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    Nothing. Sorry! But the exp(-2s) factor has to include all of F(s), i.e. you need another bracket. (Your post 3, prob. 3).
    I think you have the hang of it. Good work.
     
  8. Dec 1, 2016 #7
    thank you!
     
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