f（x）=2{（sinx/2）+[（根号3）cosx]/2} =2sin(x+π/3) 当x+π/3=2kπ+π/2、即x=π/6时、f（x）取最大值为2 当x+π/3=2kπ-π/2、即x=-5π/6时f（x）去最小值为-2