Question

If sinα + sinβ and cosα + cosβ= b, show that

cos(α+β)= $\frac{b^{2}-a^{2} }{a^{2}+b^{2} }$

Answer 1

Step-by-step explanation:

see attachment for your answer

identities :sin²x +cos²x =1

sina=+sinb =2sin(a+b/2).cos (a-b/2)

cos2a = cos²a- sin²a