（4）用作表语：To teach is to learn.
His job is to sell cars.
（5）用作状语，表示目的，结果。
We come to school to study English.（目的）
= in order to
I hurried to the store, only to find it closed.（结果）
（6）定语：不定式短语作定语须位于名词之后。
He asked for a piece of paper to write it on.
= to write it on the piece of paper.
The poor man has no house to live in.
= to live in the house.
Have you anything to do?
= to do anything
4.不定式的时态意义：
She seems to dance very well.（现在情况）
She seems to be dancing in the dancing hall.（正在进行）
She seems to have danced well.（过去情况）
Has was happy to have been staying with his uncle.（动作持续一段时间）
5.不定式语态：
The doctor recommended him to air the room.
The doctor recommended the room to be aired.
She expects the police to find her bicycle.
She expects her bicycle to be found by the police.
She felt a bit puzzled as he had asked her such a question.
She felt a bit puzzled to have been asked such a question.
6.不定式否定形式：not to do ...
He got up early in order not to miss the train.
