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Math Help - [SOLVED] Trig Equivalency question?

  1. #1
    Junior Member doomgaze's Avatar
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    [SOLVED] Trig Equivalency question?

    we know that cos^2(x) = 1/2(1+cos(2x))

    could I say that cos^2(3x)=1/2(1+cos(6x)) ?
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  2. #2
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    Quote Originally Posted by doomgaze View Post
    we know that cos^2(x) = 1/2(1+cos(2x))

    could I say that cos^2(3x)=1/2(1+cos(6x)) ?
    Difinetly you can say so.
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  3. #3
    Junior Member doomgaze's Avatar
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    Quote Originally Posted by sa-ri-ga-ma View Post
    Difinetly you can say so.
    I guess more importantly is it correct?
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    Yes.

    --Kevin C.
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    Quote Originally Posted by doomgaze View Post
    I guess more importantly is it correct?
    If 3x= t
    6x= 2t.
    cos(2t) = 2cos^2(t) - 1
    so 2cos^2(t) = 1+cos(2t)

    cos^2(t) = 1/2(1+cos(2t))

    replace t by 3x and find the result.
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