Prove the identity: [2tan(x/2)] / [1+tan^2(x/2)] = sinx
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Originally Posted by Mr_Green Prove the identity: [2tan(x/2)] / [1+tan^2(x/2)] = sinx $\displaystyle \sin x = 2\sin \frac{x}{2}\cos \frac{x}{2} = \frac{ 2\sin \frac{x}{2}\cos \frac{x}{2}}{1} = \frac{2\sin \frac{x}{2}\cos \frac{x}{2}}{\cos^2 \frac{x}{2} + \sin^2 \frac{x}{2}} = \frac{2\tan\frac{x}{2}}{1+\tan^2\frac{x}{2}}$
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