Used to do something. Point: used-past tense.

②be used to do.

Be used to do. Key points: be+used => Be done passive voice

③be used to doing.

Be used to doing sth. Point: used is an adjective, meaning "habitual".

-ing suffix-ongoing, habitual action/thing.

1, used to do something? to? do.

2. Be used to doing something? be? used? to? doing.

3. be used to do something? be? used? to? do? sth.

This is mainly to investigate the usage of the word "use". “used? to? Do "is translated as" used to do something ",which emphasizes that it is not done now. ? I used to smoke.but I've stopped. I used to smoke a lot, but I have given up now.

Past tense is a kind of English grammar, indicating an action or state that happened in a certain time in the past. Verbs in the general past tense are usually expressed in the past tense form of the verb prototype, and the past tense of the verb is changed on the basis of the verb prototype. The past tense of verbs can be divided into regular verbs and irregular verbs.