Trigonometry
Advanced

Half Angle: Cosine

Cosine of half an angle.

Formula

cos⁡θ2=±1+cos⁡θ2\cos\frac{\theta}{2} = \pm\sqrt{\frac{1+\cos\theta}{2}}

Variables

\thetaAngle

Did You Know?

The half-angle formulas were essential for building the detailed trigonometric tables of past centuries.

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