" 10."sin(n+1)x sin(n+2)x+cos(n+1)x cos(n+2)x=cos x

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

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

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

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

Prove that: sin(n+1)x sin(n+2)x+cos(n+1)x cos(n+2)x=c

Prove the following: sin (n + 1)x sin (n + 2)x + cos (n + 1)x cos (n + 2)x = cos x

Prove that sin (n+1) x sin (n +2) x + cos (n +1) x cos (n +2) x = cos x

Prove that: sin (n + 1) x sin (n + 2)x + cos (n + 1) x cos (n + 2) x = cos x

Solve for x the equation |(a^(2),a,1),(sin(n+1)x,sin nx,sin(n-1)x),(cos(n+1)x,cosn x,cos(n-1)x)|=0

Prove that (i) cos (n + 2) x cos (n+1) x +sin (n+2) x sin (n+1) x = cos x) (ii) " cos " .((pi)/(4)-x) " cos " .((pi)/(4)-y) " - sin " ((pi)/(4)-x ) " sin " ((pi)/(4) -y) =" sin " (x+y)