Where Does the Tangent Half-Angle Identity Come From?

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I saw this identity somewhere and have been looking for a derivation but I can't seem to find one. It would be of great help if someone can show me where this comes from.

tan\frac{\theta}{2} = csc\theta - cot\theta
 
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Hi Yuqing! :smile:

(have a theta: θ :wink:)

Hint: cscθ - cotθ = (1 - cosθ)/sinθ = … ? :smile:
 
Ah I see. Didn't think it was so simple.

Thank you very much.
 

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