Дмитрий Пусть: Q = ( sin(x) - cos(x)); Тогда : Q^2 = -2*sin(x)*cos(x)+1 = - sin(2*x) +1; sin(2*x) = 1- Q^2; (5*(Q^2-1) -16*Q+8 =0; Q = 1/5, 3; sin(2*x) =- Q^2+1;