2) cos²x − sin²x = 0,5;

2) cos²x − sin²x = 0,5.

cos 2x = 0,5;

2x = ±arccos 0,5 + 2πk, k ∈ Z;

2x = ±π/3 + 2πk, k ∈ Z;

x = ±π/6 + πk, k ∈ Z.

Ответ: x = π/6 + πk, x = -π/6 + πk, k ∈ Z