fx＝1/2sin2x－√3/2cos2x
=sin2xcosπ/3-cos2xsinπ/3
=sin(2x-π/3)
f(x)最小正周期T=2π/2=π
当2x-π/3=2kπ-π/2,即x=kπ-π/12,k∈Z时
f(x)取得最小值-1