y=cos2x+sinx+1=1-2sin^2x+sinx+1=-2sin^2x+sinx+2=-2(sinx-1/4)^2+(17/8)
x∈[-π/6,π/3],sinx∈[-0.5,根号3/2],
当x=1/4时,y取得最大值17/8.
当x=-0.5时,y取得最小值1.