解:设点A的坐标为(0,0),D的坐标为(x,y)则点C的坐标为(2,5),点B的坐标为(1,3)在平行四边形ABCD中,所以有AB平行CD,AC平行BD可得:AB=aCD于是有:1=a(x-2).............................13=a(y-5).............................2AC=bBD 于是有:2=b(x-1).............................35=b(y-3).............................4联立1、2、3、4解得:x=3,y=8向量AD=(x-0,y-0)=(3,8)向量BD=(x-1,y-3)... |