Geometry & Trigonometry
Intermediate

Sine Double Angle

Double-angle identity for sine.

Formula

sin⁡(2θ)=2sin⁡θcos⁡θ\sin(2\theta) = 2\sin\theta\cos\theta

Variables

\thetaAngle

Example

sin 60° = 2·sin30°·cos30° = 2·½·(√3/2) = √3/2. ✓

Did You Know?

Double-angle formulas were essential for building the first accurate trigonometric tables.

trigonometryidentitydouble angle