函数y=(1+sinx)/(2+cosx)的值域为
问题描述：
函数y=(1+sinx)/(2+cosx)的值域为
答
2y+ycosx=1+sinxsinx-ycosx=2y-1√(1+y²)sin(x+θ)=2y-1则：sin(x+θ)=(2y-1)/√(1+y²)则显然有：-1≦(2y-1)/√(1+y²)≦1即：(2y-1)²/(1+y²)≦1(2y-1)²≦y²+1 3y...