Trigonometry
Advanced

Product: cos A cos B

Product-to-sum identity.

Formula

cos⁡Acos⁡B=12[cos⁡(A−B)+cos⁡(A+B)]\cos A\cos B = \tfrac{1}{2}[\cos(A-B) + \cos(A+B)]

Variables

A,BAngles

Did You Know?

These identities explain "beats" — the throbbing you hear when two nearly-equal musical notes overlap.

product to sumidentity