2sinx-1>0sinx>0.52kπ+π/6f(x)的前键单调性与sinx相激敏反递减区间慧铅巧:(2kπ+π/6, 2kπ+π/2]递增区间:[2kπ+π/2, 2kπ+5π/6)是周期函数,周期:2π
2sinx-1>0,sinx>1/2,x>30度