2-cosα>0,無(wú)論α取何值,分式恒有意義,函數(shù)定義域?yàn)镽.
整理,得
2y-ycosα=sinα-3
sinα+ycosα=2y+3
√(1+y²)sin(α+β)=2y+3 其中,tanβ=y
sin(α+β)=(2y+3)/√(1+y²)
-1≤sin(α+β)≤1
-1≤(2y+3)/√(1+y²)≤1
(2y+3)²/(1+y²)≤1
整理,得
3y²+12y≤-8
(y+2)²≤4/3
-2-2√3/3≤y≤2√3/3 -2
函數(shù)的值域?yàn)閇-2 -2√3/3,2√3/3 -2]