cos4x-sin2x=0 cos²2x-sin²2x-sin2x=0 1-2sin²2x-sin2x=0 2sin²2x+sin2x-1=0 sin2x=(-1±3)/4 1) sin2x=-1 => 2x=-π/2+2πn => x=-π/4+πn 2) sin2x=½ => 2x=(-1)^n*π/6+πn => x=(-1)^n*π/12+(π/2)•n x₁=3π/4, x₂=5π/12
