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Thread: trig help...

  1. May 26th 2009, 04:33 PM #1
    Valaina
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    trig help...

    cos(alpha - beta) cos(alpha + beta) = cos squared alpha - sin squared beta
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  2. May 26th 2009, 04:56 PM #2
    skeeter
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    Quote Originally Posted by Valaina View Post
    cos(alpha - beta) cos(alpha + beta) = cos squared alpha - sin squared beta
    use the sum/difference identity for cosine ...

    \cos(a \pm b) = \cos(a)\cos(b) \mp \sin(a)\sin(b)

    btw ... this should have been posted in the trig section.
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