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Using angle sum-difference, double, and/or triple angle relations with tangent, cosine, and sine, need help proving tangent half-angle relations. Thanks!

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Your title helped me get to the correct wikipedia page. – Leo Sep 5 '14 at 13:18

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You can find these proofs on Wikipedia.

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Man I searched the entire internet for this and its on wikipedia? Thank you for posting this. I just did not understand why the "usual" tangent half-angle identity tan x/2 = (1-cos x)/ sin x is true. Thanks! – Leo Sep 5 '14 at 13:17

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