Trigonometry
Intermediate

Cosine of a Difference

Angle subtraction formula for cosine.

Formula

cos⁡(A−B)=cos⁡Acos⁡B+sin⁡Asin⁡B\cos(A-B) = \cos A\cos B + \sin A\sin B

Variables

A,BAngles

Did You Know?

Ptolemy tabulated chords equivalent to these formulas around 150 AD to predict planetary motion.

subtractionidentity