f(x)=2sinx[(√3/2)cosx－(1/2)sinx]－cos2x＋m
=√3sinxcosx－sin²x－cos2x＋m
=(√3/2)sin2x－(1/2)＋(1/2)cos2x－cos2x＋m
=sin(2x－30°)＋m－(1/2)周期为π.