# Sum of Two Angles Identities (Visual Proof)

This figure illustrates the “proof without words” of the sum of two angles identities. To construct this figure: see this example.

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The sum of two angles identities express the cosine and sine of the sum of two angles in terms of their individual cosine and sine components.

To derive the sum of two angles identities, two right triangles are placed next to eachother so their angles sum together, then their proportions are related together.