Trigonify

Sum to Product

cos A + cos B

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

Related Sum to Product identities

sin A + sin Bsin A - sin Bcos A - cos B

Study this and 44 more identities in the Trigonify workspace — an interactive unit circle, a step-by-step triangle solver, quizzes, and a practice problem bank.