cos2x≤cos3x-cos4x
cos2x+cos4x≤cos3x
2cos3x cosx≤cos3x, 2cos3x cosx-cos3x≤0
cos3x(2cosx-1)≤0
1){cos3x≤0 2) {cos3x>0
{2cosx-1>0 {2cosx-1≤0
{ π/2+2πn≤ 3x ≤3π/2+2πn {-π/2+2πm<3x<π/2+2πm </p>
{ cosx>1/2 { cosx≤1/2
{π/6+2πn/3≤x≤π/2+2πn/3 {-π/6+2πm/3
{-π/3+2πk
Теперь объедини решения систем