y'=1-2cosx 0<=X<=2π
令y'>0
解得π/3≤x≤5π/3
单调曾区间π/3≤x≤5π/3
同理令y'<0
0≤x≤π/3 或5π/3≤x≤2π
单调减区间0≤x≤π/3 或5π/3≤x≤2π
极小值 x=π/3时取得 π/3-√3
极大值x=5π/3时取得 5π/3+√3