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Homework Help: Trig Please Help me

  1. Jul 21, 2010 #1
    1. The problem statement, all variables and given/known data

    What does cis^-1 (x) mean
    like you know how there is sin^-1 (x) and sin(x) applying that concept with cis(x) what does that mean?

    Note that is not a spelling mistake I'm not trying to say cos^-1 (x) I'm indeed saying cis^-1 (x) with an "i"

    I also wander what does cis stand for like cos is cosine sin is sine etc. how do I say cis...

    like I was thinking ok

    cis(x) = cos(x) + i sin(x) = e^(ix)
    what does cis^-1(x) mean

    kind of stuck here...

    Thank You

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Jul 21, 2010 #2
    Since cis(x) is defined in the following manner,

    [tex]cis(x) = cos(x) +isin(x) = e^{ix}[/tex]

    Simply take the inverse of cis(x),

    [tex]cis^{-1}(x) = \pm cos^{-1}(\frac{x^{2} + 1}{2x})[/tex]
    Last edited: Jul 21, 2010
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