Geometry & Trigonometry
Advanced

Tangent Double Angle

Double-angle identity for tangent.

Formula

tan⁡(2θ)=2tan⁡θ1−tan⁡2θ\tan(2\theta) = \frac{2\tan\theta}{1 - \tan^2\theta}

Variables

\thetaAngle

Example

tan 90° is undefined because tan 45° = 1 makes the denominator 1−1 = 0.

Did You Know?

The tangent double-angle formula is essential for deriving many calculus integration tricks.

trigonometryidentitydouble angle