Locate the infinitive. Since it is used as a noun, determine its noun use.

To tell a lie frustrates honest people.

Infinitive:

Use:

Infinitive: To tell a lie

Use: to describe what is frustrating the honest people

Infinitive: to tell.

Use: subject.

Explanation:

An infinitive is a verbal made up of to + verb form that can be used as a noun. In the sentence to tell a lie frustrates honest people, the inifinitive is to tell, and it is used as the subject of the sentence since to tell is the thing about whom the statement is made.

In this case, the noun infinitive is followed by a direct object (a lie,) but could also be followed by a predicate nominative, a predicate adjective or any other modifier.