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Proof [itex]sin(\frac{x}{2}) = \pm \sqrt{\frac{1-cos(x)}{2}}[/itex]

Simple issue really i'd think but i can't come up with a way.

For starters i'd use however

[itex]cos^2(x) + sin^2(x) = 1[/itex] identity.

Which evidently would lead into

[itex]sin(\frac{x}{2}) = \pm \sqrt{1-cos^2(\frac{x}{2})}[/itex]

But then i got nothing...

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# Homework Help: Problem with sin(x/2) proof

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