brother, you are too careless,they should be:

来源: 于 2010-08-26 16:00:09 [旧帖] [给我悄悄话] 本文已被阅读：次

which is bigger,y or (xd)^2. If the room is rectangle floor
...............y or x^2*z^2*d^2,If room is circle floor...It is interesting question.