Half-angle formulas for tangent for JEE

Formula

\(\tan\dfrac{A}{2}=\pm\sqrt{\dfrac{1-\cos A}{1+\cos A}}=\dfrac{\sin A}{1+\cos A}=\dfrac{1-\cos A}{\sin A}\)

Variables: \(A\) = angle.

Conditions: Sign depends on quadrant of \(A/2\); denominators nonzero.

Substitution, simplification, proving identities.