Question

Prove the following​

Answer 1

Answer:

put, π/4-x=A

π/4-y=B

Taking LHS

cosAcosB-sinAsinB

=cos(A+B)

=cos[π/4-x+π/4-y]

cos[π/2-(x+y)]

sin(x+y). [by using cos(90°- A)]