令,Y=(sin x-1)/(cos x+2) Y*cosx+2y=sinx-1,sinx-ycosx=2y+1,√(1+y^2)*sin(x-b)=2y+1,sin(x-b)=(2y+1)/[√(1+y^2)]而,-1≤sin(x-b)≤1,即,-1≤(2y+1)/[√(1+y^2)]≤1.-4/3≤Y≤0.(sin x-1)/(cos x+2) 则,值域为:[-...