这个是我做的步骤~

把 派 记为“pi”哦~ 根号3记为'3~~f(x)=2cos(x+pi\4)cos(x-pi\4)+'3sin2x =-2cos(x+pi\4)sin(x+pi\4)+'3sin2x =-sin(2x+pi\4)+'3sin2x ='3sin2x-sin(2x+pi\4) =2sin(2x-pi\6)所以、f(x)的范围是-2到2周期T=2pi\2=pi