sinx,cosx是方程4x^2-4mx+2m-1=0的两个根
sinx+cosx=m
sinx*cosx=(2m-1)/4
1+2sinx*cosx=m^2
1+(2m-1)/2=m^2
2m^2-2m-1=0
(m-1/2)^2=3/4
m-1/2=±√3/2
m=1/2±√3/2
3π/2＜x