This post includes proofs of two angle addition identities.

$ \sin(x+y) = \sin x \cos y + \sin y \cos x$

$ \cos(x+y) = \cos x \cos y – \sin x \sin y$

**References**

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Trigonometry# Angle Addition Identities

This post includes proofs of two angle addition identities.

$ \sin(x+y) = \sin x \cos y + \sin y \cos x$

$ \cos(x+y) = \cos x \cos y – \sin x \sin y$

**References**