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Homework Help: Convert harmonic equation to polar form

  1. Jan 15, 2008 #1


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    1. The problem statement, all variables and given/known data

    [tex] cos(7 t) + sin(7 t)[/tex]
    into polar form of
    [tex]A cos(\omega_0 t - \delta)[/tex]

    This is a review problem where once we convert this to polar form we are to give amplitude, period and delay (shift). I can answer this question if someone can point me to a website tutorial that tells the process of converting this problem. I really dont expect someone to answer this for me because I need to learn how to do it on my own.

    3. The attempt at a solution

    I have not made an attempt as of yet, however i know there is a trig identity
    cos(x)cos(y) + sin(x)sin(y) = cos(x-y)

    I was given this advice BUT I dont know what to do because:
    cos(7)cos(t) doesnt equal cos(7t) .... right?
    Last edited: Jan 15, 2008
  2. jcsd
  3. Jan 15, 2008 #2


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    Homework Helper

    Let [itex]Acos(\theta-\delta)=cos(7t)+sin(7t)[/itex] then just equate and solve
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