Question

sin(n+1)xsin(n+2)x+cos(n+1)xcos(n+2)=cosx​

Answer 1

Answer:

cosx { since cos(-x) = cosx }

Step-by-step explanation:

==>We have cos(n+1)xcos(n+2)x + sin(n+1)xsin(n+2)x it is from the identity

===>cos(a-b) = cosa * cosb + sina * sinb

====>here a= (n+1)x  and b= (n+2)x

so

==> cos((n+1)x-(n+2)x)

===> cos(nx+x-nx-2x)

===> cos(-x)

===> cosx { since cos(-x) = cosx }