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Math Help - prove the identity

  1. #1
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    prove the identity

    Prove the identity:

    [2tan(x/2)] / [1+tan^2(x/2)] = sinx
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  2. #2
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    Quote Originally Posted by Mr_Green View Post
    Prove the identity:

    [2tan(x/2)] / [1+tan^2(x/2)] = sinx
    \sin x = 2\sin \frac{x}{2}\cos \frac{x}{2} = \frac{ 2\sin \frac{x}{2}\cos \frac{x}{2}}{1} = \frac{2\sin \frac{x}{2}\cos \frac{x}{2}}{\cos^2 \frac{x}{2} + \sin^2 \frac{x}{2}} = \frac{2\tan\frac{x}{2}}{1+\tan^2\frac{x}{2}}
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