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Heaviside/step function question

  1. Apr 21, 2010 #1
    1. The problem statement, all variables and given/known data
    Hey so this is a really trivial question.

    f(t) = { 0, 0<= t < pi
    { -sin3t, t>=pi

    Just having trouble properly shifting this!

    3. The attempt at a solution

    f(t) = -upi(t)sin(3t)

    = -upi(t)sin[3(t-pi+pi)]

    = upi(t)sin[3(t-pi+pi)]

    How do I take the +pi out?
    I know it should end up as:


    I just don't really understand how from my last step.
    thanks for reading!
  2. jcsd
  3. Apr 21, 2010 #2


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    What happened to the minus sign?
    Hint: 3(t-pi+pi)=3(t-pi)+3pi
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