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Math Help - Need someone to check LT

  1. #1
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    Need someone to check LT

    i have signal as shown on the attached image, and i need to introduce it analytically and apply Laplace transformation on it...

    signal is :
    Need someone to check LT-signal.jpg

    and i have done this


    \displaystyle f(t) = 10\cdot t \cdot u(t) - 20 \cdot (t-10) \cdot u(t-10) +10\cdot (t-20) \cdot u(t-20)

    that's as far as writting it analytically... (is this correct ? )

    now with LT ...

    \displaystyle F(S)= 10 S \frac {1}{S} -20e^{-10S} \frac {1}{S}  + 10 e^{-20S} \frac {1}{S}  =


    =10 - 20 e^{-10S}\frac {1}{S}  + 10 e^{-20S}\frac {1}{S}


    P.S. sorry for bad image
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  2. #2
    A Plied Mathematician
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    You need to crunch your f(t) down a bit. The correct formula is yours divided by 10. How does that change your LT?
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  3. #3
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    Quote Originally Posted by Ackbeet View Post
    You need to crunch your f(t) down a bit. The correct formula is yours divided by 10. How does that change your LT?
    aaaah, my bad... it's not 10t.....

    i get :

     f(t) = t u(t) - 2 (t-10) u(t-10) + (t-20)u(t-20)

    so LT is

     F(S) = 1 - 2e^{-10s} \frac {1}{s} + e^{-20s} \frac {1}{s}

    is that it ?
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  4. #4
    A Plied Mathematician
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    Here's a way to check it for yourself. WolframAlpha is a great website.
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  5. #5
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    Quote Originally Posted by Ackbeet View Post
    Here's a way to check it for yourself. WolframAlpha is a great website.
    thank you
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  6. #6
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    You're welcome. Have a good one!
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