f(x)=2/√3*(sin2x*1/2-cos2x*√3/2)
=2/√3*(sin2xcosπ/3-cos2xsinπ/3)
=2/√3*sin(2x-π/3)
最大则sin(2x-π/3)=1
2x-π/3=2kπ+π/2
x=kπ+5π/12