Sin7x +Cos²2x -Sin²2x -Sinx =0;
Sin7x +Cos4x -Sinx = 0
(Sin7x - Sinx) + Cos4x = 0
2Sin3xCos4x + Cos4x =0
Cos4x(2Sin3x +1)=0
Сos 4x = 0 или 2sin3x +1 = 0
4x = π/2 + πk , k ∈Z Sin3x = -1/2
x = π/8 + πk/4, k ∈Z 3x = (-1)^(n+1) π/6 + nπ, n ∈Z
x = (-1)^(n+1)π/18 + nπ/3, n ∈Z