求函数y=(1-sinx)/(3+2cosx)的最大值与最小值

y = (1-sinx)/(2cosx+3) ≥ 0
∵1-sinx = 2ycosx+3y
2ycosx+sinx = 1-3y
√[(2y)²+1] sin(x+T) = 1-3y 。tanT=2y
1-3y≤√[(2y)²+1]
1-6y+9y²≤4y²+1 ∴5y²-6y=y(5y-6)≤0 ∴ 0≤y≤6/5