：
不定式的特殊句型so as to
1) 表示目的；它的否定式是so as not to do。
Tom kept quiet about the accident so as not to lose his job.汤姆对事故保持沉默是为了不丢掉他的工作。
Go in quietly so as not to wake the baby. 轻点进去，别惊醒了婴儿。
2) so kind as to ---劳驾
Would you be so kind as to tell me the time? 劳驾，现在几点了。
不定式的特殊句型Why not
"Why not +动词原形"表达向某人提出建议，翻译为："为什么不……?" "干吗不……?"
例如：Why not take a holiday?干吗不去度假？
不定式的时态和语态
时态语态主动被动一般式to doto be done进行式to be doing完成式to have doneto have been done完成进行式to have been doing
