Question

If SinA+SinB=a and CosA+CosB, then Cos(A+B) is equal to
A. a^2+b^2/b^2-a^2
B. 2ab/a^2+b^2
C. b^2-a^2/a^2+b^2
D. a^2-b^2/ a^2+b^2

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Answer 1

Answer:

A. a^2+b^2/b^2-a^2 is the correct answer