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Math Help - Trig identity?

  1. #1
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    Exclamation Trig identity? (new one)

    I need help with this one...
    sin3A+cos3A/sinA + CosA = 1-sinAcosA
    Thanks
    Last edited by WhatthePatel; November 10th 2012 at 03:24 PM.
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  2. #2
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    Re: Trig identity?

    Quote Originally Posted by WhatthePatel View Post
    I need help with this one...
    sin3A+cos3A/sinA + CosA = 1-sinAcosA
    Hint:
    x^3+y^3=(x+y)(x^2-xy+y^2)
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  3. #3
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    Re: Trig identity?

    New identity?
    sin3x = 3cos2xsinx-sin3x
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  4. #4
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    Re: Trig identity?

    \sin(3x) = \sin(2x+x) = \sin(2x)\cos(x) + \cos(2x)\sin(x)

    finish it using appropriate double angle identities.

    ... and, start a new thread for a new problem.
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