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Precalculus · F-TF

Sum and Difference Identities — sin(A±B), cos(A±B)

sin(A+B) = sinA cosB + cosA sinB; cos(A+B) = cosA cosB − sinA sinB. Difference: flip the sign on the second term.

PrecalculusCommon Core HSF-TF.C.9F-TFVerified correct ✓

Worked examples

Use a sum or difference identity to evaluate cos(30° + 45°). Round to 4 decimal places.
Answer: 0.2588
Use a sum or difference identity to evaluate sin(30° + 60°). Round to 4 decimal places.
Answer: 1

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