a-b=(sina-√3,cosa-3)则〡a-b〡^2=(sina-√3)^2+(cosa-3)^2=sina^2-2√3sina+3+cosa^2-6cosa+9=13-2√3(sina+√3cosa)=13-4√3sin(a+π/3))∈[13-4√3,13+4√3]=[(2√3-1)^2,(2√3+1)^2]所以〡a-b〡∈[2√3-1,2√3+...