Trigonometry
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Sum to Product: cos A + cos B

Sum-to-product identity.

Formula

cos⁡A+cos⁡B=2cos⁡A+B2cos⁡A−B2\cos A + \cos B = 2\cos\tfrac{A+B}{2}\cos\tfrac{A-B}{2}

Variables

A,BAngles

Did You Know?

Fourier showed that any repeating signal is a sum of cosines and sines like these — the basis of MP3 and JPEG.

sum to productidentity