OQ=PQ+x PC+y PA x =y=-1/2
PA=x PO+y PQ+PD x=2,y=-2
[取坐标系A﹙000﹚ B﹙200﹚ D﹙020﹚ P﹙11a﹚
OQ=PQ+x PC+y PA 即﹛010﹜=﹙0,1,-a﹜+﹛x,x,-ax﹜+﹛-y,-y,-ay﹜……]
OQ=PQ+x PC+y PA x =y=-1/2
PA=x PO+y PQ+PD x=2,y=-2
[取坐标系A﹙000﹚ B﹙200﹚ D﹙020﹚ P﹙11a﹚
OQ=PQ+x PC+y PA 即﹛010﹜=﹙0,1,-a﹜+﹛x,x,-ax﹜+﹛-y,-y,-ay﹜……]