A、v<sub>e</sub>=BD·<img width="28" height="23" src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/1c29d00c-1425-4dbb-8235-b2f3a9b6fab7.png" />，方向垂直AB
B、v<sub>e</sub>=R·<img width="16" height="15" src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/a3918461-9a71-437d-ae54-25c87b7c8590.png" />，方向平行EB
C、v<sub>e</sub>=BC·<img width="28" height="23" src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/1c29d00c-1425-4dbb-8235-b2f3a9b6fab7.png" />，方向垂直BC
D、v<sub>e</sub>=R·<img width="16" height="15" src="http://admintk.100xuexi.com/UpLoadImage/2013-05-07/a3918461-9a71-437d-ae54-25c87b7c8590.png" />，方向平行BA