Решаем подстановкой: х =π-y
Sin(π-y) - Cosy = -1
Siny - Cosy = -1
Cos(π/2 - у) - Сosy = -1
-2Sinπ/4 * Sin(π/4 - y) = -1
√2Sin(π/4 - y) = 1
Sin(π/4 - y ) = √2/2
π/4 - y = (-1)^n π/4 + nπ , n ∈Z
y = π/4 + (-1)^n *π/4 - nπ, n ∈Z
x = π- y = π - ( π/4 + (-1)^n *π/4 - nπ) , n ∈Z
x = 3π/4 -(-1)^n*π/4 + nπ, n ∈Z