题目错了一个字母，改正后为： y=√3cos(3/2π+2x)+cos²x-sin²x =√3sin2x+cos2x =2sin(2x+π/6)当2x+π/6=π/2+2kπ,即x=π/4-π/12+kπ（k属于Z）,y最大=2当2x+π/6=-π/2+2kπ,即x=-π/4-π/12+kπ（k属于Z）,y最大=-2
