y=[(sinx)^4-(cosx)^4]+[(2根号3)*(sin2x)/2]
=[(sinx)^2+(cosx)^2][(sinx)^2-(cosx)^2]+(根号3)sin2x
=[(根号3)sin2x]-cos2x
=2sin[2x-(pi/6)]
所以T=2pi/2=pi
y(min)=-2
递增区间：(-pi/2)+2kpi