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Math Help - Piecewise Laplace 3

  1. #1
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    Piecewise Laplace 3



    Here is my answer:

    step(t-1)-6*step(t-3)+9*step(t-5)

    but it's wrong!!
    help!!
    Last edited by Phyxius117; December 2nd 2009 at 06:40 PM.
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  2. #2
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    Quote Originally Posted by Phyxius117 View Post


    Here is my answer:

    step(t-1)-6*step(t-3)+9*step(t-5)

    but it's wrong!!
    help!!
    Note as quick check when you evaluate at t=4 you get
    f(4)=1-6+0=-5

    Just "turning on" the next part is not enough you need to "turn off" the first part as well.
    Let S(t) be the unit step function then

    f(t)=S(t-1)-7S(t-3)+15S(t-5)

    Note to fit the turn on and off analogy from above

    f(t)=S(t-1) - S(t-3)-6S(t-3)+6S(t-5)+9S(t-5)

    When you simplify it is the same as above.
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