To have to

[Iouri]

Here http://www.dutchgrammar.com/en/?n=Verbs.au09
I found that when hebben is used in the meaning to have to it always takes te

Is it correct:

Ik heb te gaan - I have to go
Hij heeft het te doen - He has to do it

Also it is mentioned that
Because a past participle cannot serve as an auxiliary verb, we have to use infinitives instead. In the perfect tense, we drop te.

In perfect tens we use hebben + past participle
IN case of have to we use hebben + te + infinitive

In this example
Hij heeft niet in het openbaar durven spreken. He has not dared to speak in public.
how to determine if it is present perfect or have to construction with dropped te.

bedankt

[ngonyama]

Here http://www.dutchgrammar.com/en/?n=Verbs.au09
I found that when hebben is used in the meaning to have to it always takes te

Is it correct:

Ik heb te gaan - I have to go
Strictly speaking: yes it correct, but we would hardly ever say it that way. "Ik moet gaan" or "Ik moet weg" are common ways of saying this
Hij heeft het te doen - He has to do it
Yes that is correct. However, it is very strong, even menacing as in "otherwise I'll break his legs" or so. Often the word "maar" is used : Hij heeft het maar te doen: No matter what his objections, he'll have no choice. Resistance is futile!

Also it is mentioned that
Because a past participle cannot serve as an auxiliary verb, we have to use infinitives instead. In the perfect tense, we drop te.

In perfect tens we use hebben + past participle
IN case of have to we use hebben + te + infinitive

In this example
Hij heeft niet in het openbaar durven spreken. He has not dared to speak in public.

how to determine if it is present perfect or have to construction with dropped te.

This sentense is the equivalent of:
Hij heeft niet gedurfd om in het openbaar te spreken.
It is the perfect of:
Hij durft niet in het openbaar te spreken.

I don't think we ever use the "must" construction of "hebben te" in the perfect.

bedankt

[Iouri]

Thank you very much