f(x)=2√3sinxcosx+2(cosx)^2-1＝根号3sin2x+cos2x=2sin(2x+Pai/6)
最小正周期T＝2Pai/2=Pai
单调减区间是2kPai+Pai/2<=2x+Pai/6<=2kPai+3Pai/2
即：〔kPai+Pai/6,kPai+2Pai/3]