Trigonify

Product to Sum

sin · sin

sin⁡αsin⁡β=12[cos⁡(α−β)−cos⁡(α+β)]\sin\alpha \sin\beta = \tfrac{1}{2}[\cos(\alpha-\beta) - \cos(\alpha+\beta)]

Related Product to Sum identities

sin · coscos · cos

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.