12. Сравнить числа cos(−5π/8) и cos(3π/4).

cos(−5π/8) = cos(5π/8) = −cos(3π/8) ≈ −0.383, а cos(3π/4) = −√2/2 ≈ −0.707. Поэтому cos(−5π/8) > cos(3π/4).