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This is a mistake right?

  1. Oct 1, 2013 #1
    The highlighted in yellow is a mistake, right? I might be going insane.

    Where does the PI go?
     

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  2. jcsd
  3. Oct 1, 2013 #2

    Office_Shredder

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    [tex] \cos(4(t+\pi)) = \cos(4t+4\pi) = \cos(4t) [/tex]
     
  4. Oct 1, 2013 #3

    SteamKing

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    Remember, sin and cos are periodic functions with period 2k*pi, k = integer.
     
  5. Oct 2, 2013 #4
    @Office_Shredder: Opps. Nice catch.

    @SteamKing: Isn't the period 2pi/k where k is the coefficient of t?
     
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