y=(sinx-2)/(cosx+1)的值域

y=(sinx-2)/(cosx+1) ycosx+y=sinx-2 ycosx-sinx=-2-y √[y+(-1)]sin(x+θ)=-2-y √扒袭(1+y)sin(x+θ)=-2-y sin(x+θ)=(-2-y)/√(1+y) -1≤sin(x+θ)≤1 -1≤橡迟(-2-y)/√(1+y)≤1 y≤春如兄-3/4 值域：(-∞，-3/4]