OpenStax, Algebra and Trigonometry 2e §9.4 Sum-to-Product and Product-to-Sum Formulas · Exercise 55 · Trigonometry · Compound & multiple angles

Sum-to-Product and Product-to-Sum Formulas · Exercise 55

Prove the following sum-to-product formulas.

$cos x + cosy = 2 cos (\frac{x + y}{2}) cos (\frac{x - y}{2})$

~11 minWritten answer · compare with the solution

OpenStax, Algebra and Trigonometry 2e · §9.4 Sum-to-Product and Product-to-Sum Formulas · Exercise 55

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