Question

sin(n+1)×sin(n+2)×+cos(n+1)×cos(n+2)×=cos×​

Answer 1

Answer:

Step-by-step explanation:

lhs

sin(n+1)x*sin(n+2)x+cos(n+1)x*cos(n+2)x         [sinA*sinB+cosA*cosB=cos(A-B)]

cos(n+1-n-2)x

cos(-1)x                    

cosx    =rhs  

proved