The following formulas relate the sum of trigonometric functions of different angles to products of multiple angle functions. These identities are also useful for simplifying expressions.

sin(α) + sin(β) = 2 sincos    

cos(α) + cos(β) = 2 coscos    

sin(α) - sin(β) = 2 cossin    

cos(α) - cos(β) = - 2 sinsin    

PLUS

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