Sum and Difference Identities

Question 1

What are the Sum Identities?

Answer 1

sin(A + B) = sin A cos B + cos A sin B.
cos(A + B) = cos A cos B - sin A sin B.
tan(A + B) = (tan A + tan B)/(1 - tan A tan B).

Question 2

What are the Difference Identities?

Answer 2

sin(A - B) = sin A cos B - cos A sin B.
cos(A - B) = cos A cos B + sin A sin B.
tan(A - B) = (tan A - tan B)/(1 + tan A tan B).