过程省略向量2字：AO·AB=BO·BA,即：AO·AB+BO·AB=AB·(AO+BO)=0,即：AB·(OA+OB)=0而在△AOB中,假设AB边的中点为D,则：OA+OB=2OD,故：AB·OD=0说明AB边与AB边的中线OD垂直,即：AB边的中线即AB边的中垂线,故：|OA|...