Question

Which of the following identity is not true?

(A) cosxcosy=1/2(cos(x+y)+cos(x−y))

(B) sinxsiny=1/2(cos(x+y)+cos(x−y))

(C) sinxsiny=1/2(cos(x−y)−cos(x+y))

(D) sinxcosy=1/2(sin(x+y)+sin(x−y))

Answer 1

Answer:

option: (B)

Step-by-step explanation:

1/2(cos(x+y)+cos(x-y)) = cosx.cosy