Sin2x-cosx=0

cos7x+cosx=0

1) 2Sin x Cos x - Cos x = 0

Cos x (2Sin x - 1) = 0

Cos x = 0 или 2Sin x - 1 = 0

x = π/2 + πk, k∈Z Sin x = 1/2

x = (-1) ^n arcSin 1/2 + nπ, n∈Z

x = (-1) ^n π/6 + πn, n∈Z

2) 2Cos 4x Cos 3x = 0

Cos 4x = 0 или Сos 3x = 0

4 х = π/2 + πk, k∈Z 3 х = π/2 + πk, k∈Z

x = π/8 + πк/4, к∈Z х = π/6 + πк/3, к∈Z