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Math Help - help with a proof

  1. #1
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    help with a proof

    the proof is sin^5(x)cos^2(x) = (cos^2(x) - 2cos^4(x) + cos^6(x))sin(x)

    i'd like to say where i started but nothing i've tried has come even close so im missing an identity or common sense or something. any help or a shove in the right direction would be great. thanks so much.
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  2. #2
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    Re: help with a proof

    It is quite simple just write sin^2 (x) = 1-cos^2 (x)
    LHS = sin^5 (x) cos^2 (x) = sin x sin^4 (x) cos^2 (x) = sin x ( 1 - cos^2 (x) )^2 cos^2 (x) Just simplify and you would get the result.
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  3. #3
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    Re: help with a proof

    thanks much mate, i was making it out to be harder than it really was in my head i guess.
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