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Math Help - simple trig identity

  1. #1
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    simple trig identity

    I don't understand why:

    (cosx)^2 (sinx)^2 = (1/4)(sin2x)^2

    what identities are used here?

    Thanks!
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  2. #2
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    \sin 2x = 2\sin x\cos x
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  3. #3
    Junior Member
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    (cosx)^2 = ( (1 + cos2x) / 2 )

    (sinx)^2 = ( (1 - cos2x) / 2 )

    then, in the end

    1 - (cos2x)^2 becomes (sin2x)^2
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