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Homework Help: Harmonics and fundamental frequency questions

  1. Jul 14, 2007 #1
    I'm having a bit of a difficulty trying to determine the fundamental frequency in a given function and the harmonics.
    In the equation below,would the fundamental frequention be 1 (corresponding to the value cos(1x-pi)) and the harmonics amplitude 3 and -4?Also,the values of the frequency of the harmonic are equal (both 3),so how would it be represented in the domain frequency?

    Considering x=w0t

    v(t)=3sin(3x) - 4cos(3x) + cos(x-pi)

    cos(x-pi)=cosx (is this right??),so

    v(t)=3sin(3x) - 4cos(3x) + cos(x)

    Thanks in advance for the reply!
  2. jcsd
  3. Jul 14, 2007 #2


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    Science Advisor

    No, it's not right.
    In particular, if x= pi, cos(pi-pi)= cos(0)= 1 but cos(pi)= -1.
    What is true is that cos(x- pi)= -cos(x).

  4. Jul 14, 2007 #3

    So,conseidering what you've said,the equation would be:

    v(t)=3sin(3x) - 4cos(3x) - cos(x)

    And what about what this:

    Am i right?
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