f(x)=cos²x+2√3 sinxcosx-sin²x
=cos2x+√3sin2x
=2 [1/2cos2x+√3/2sin2x]
=2(sinπ/6cos2x+cosπ/6sin2x)
=2sin(2x+π/6)
所以
周期=2π/2=π
最大值=2
最小值=-2