Решите неравенство cos5xcos4x+sin5xsin4x

Cos5x cos4x + sin5x sin4x <√3/2
cos(5x-4x) <√3/2
cosx <√3/2
π/6 + 2πn < x < (2π -π/6) +2πn, n∈Z
π/6+2πn < x < 11π/6 + 2πn, n∈Z

cos5x*cos4x + sin5x*sin4x< (√3) /2
cos(5x-4x)< (√3) /2
cosx< (√3) /2
cosx < (√3) /2
π|6 +2πn<x<(2π -(π/6)) +2πn, nэZ
π/6+2πn<x<11π/6+2πn,nэZ