f(x)=2√3sinxcosx +2cos²x-1 =√3sin2x+ 1+ cos2x-1 ==√3sin2x+cos2x =2sin(2x+π/6） 最小正周期=πx【0，π／2】 2x+π/6【π/6，7π/6】最大值为2 最小值为02kπ+π/2<2x+π/6<2kπ+3π/2kπ+π/6
