齿轮每分钟120转，如果n表示转数，t表示转动时间．

   Television is good. You’d like to watch it all day and all night. But too much TV is a very bad thing. Scientists found that kids who watch too much TV may have more trouble learning to read. They can’t focus on their work.
   Kids learn language skills best by reading, talking and playing with others. If they spend too much time watching TV, they’ll have less time for those things. Watching too much TV is bad for people’s health. People don’t move much while watching TV. What’s more, they may eat a lot of food while watching. This can make them fat. We call these people couch potatoes.
   Fighting on TV is a big problem for kids. Yong people are good at following. Scientists have found that those who watch a lot of fighting shows are more likely to fight.

如图，在⊙O中，AC与BD是圆的直径，BE⊥AC，CF⊥BD，垂足分别为E、F

（1）四边形ABCD是什么特殊的四边形？请判断并说明理由；

（2）求证：BE=CF．