9. Упростите: (cos x + cos(π/2 + x))/(2 cos²x - sin 2x)

cos(π/2 + x) = -sin x sin 2x = 2 sin x cos x (cos x - sin x) / (2 cos²x - 2 sin x cos x) = (cos x - sin x) / (2 cos x (cos x - sin x)) = 1 / (2 cos x) Ответ: B) 1/(2 cos x)