ответ: 2+√2
Пошаговое объяснение:
2×(cosπ/8+sinπ/8)²=2×(cos²π/8+2×cosπ/8×sinπ/8+sin²π/8)
=2×(1+2cosπ/8×sinπ/8)=2×(1+sin2×(π/8)=
2×(1+sinπ/4)=2×(1+√2/2)=2+√2
