2cos^2 (3x) + sin5x = 1

Sin 5x = 1 - 2Cos² 3x

Sin 5x = - Cos 6x

Sin 5x + Cos 6x = 0

Sin 5x + Sin (π/2 - 6x) = 0

2Sin (π/4 - х/2) Сos (11x/2 - π/4) = 0

а) Sin (π/4 - х/2) = 0 или б) Cos (11x/2 - π/4) = 0

π/4 - х/2 = πn, n∈Z 11x/2 - π/4 = π/2 + πк, к ∈Z

-x/2 = πn + π/4, n ∈Z 11x/2 = π/2 + π/4 + πк, к∈Z

x = - 2πn - π/2, n ∈Z x = 3π/22 + 2πк/11, к ∈Z