cos2x+sin²x=0.5

cos²х - sin²x + sin²x = 0,5

cos²х= 0,5

cosх₁ = - 1/√2

х₁₁ = 3π/4 + 2πn

x₁₂ = - 3π/4 + 2πn

cosх₂ = 1/√2

x₂₁ = π/4 + 2πn

x₂₂ = -π/4 + 2πn