cos=a*b/(|a||b|)=a*b/(2*1)=a*b/2f(x)=a*b=根号3*sin2x-cos2x=2(根号3*sin2x/2-cos2x/2)=2(sin2xcosπ/6-cos2xsinπ/6)=2sin(2x-π/6)当f(x)取得最大值时f(x)max=2所以cos=1所以a和b的夹角是0°另外我们可以不用求,...