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Math Help - Trig: Compound Angle Formulas

  1. #1
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    Trig: Compound Angle Formulas

    Can someone explain to me how you would solve this question:

    cos23(pi)
    -------
    12

    please and thank you!
    Last edited by skeske1234; March 25th 2009 at 01:03 PM.
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  2. #2
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    Quote Originally Posted by skeske1234 View Post
    Can someone explain to me how you would solve this question:

    cos2(pi)
    -------
    12

    please and thank you!
    Hi

    Do you mean \cos \frac{2\pi}{12} or \frac{\cos 2\pi}{12} or anything else ?
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  3. #3
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    Quote Originally Posted by running-gag View Post
    Hi

    Do you mean \cos \frac{23\pi}{12} or \frac{\cos 23\pi}{12} or anything else ?
    I mean:

    \cos \frac{23\pi}{12}

    please, thanks
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  4. #4
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    Quote Originally Posted by skeske1234 View Post
    I mean:

    \cos \frac{23\pi}{12}

    please, thanks
    \cos \frac{23\pi}{12} = \cos \left(-\frac{\pi}{12}\right) = \cos \frac{\pi}{12}

    Then using \cos 2a = 2 \cos^2 a - 1 and \cos \frac{\pi}{6} = \frac{\sqrt{3}}{2} you can compute \cos \frac{\pi}{12}
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