Locate the complete infinitive phrase and identify its use.

Tom and Tim decided to spend the afternoon tobogganing.

infinitive phrase: to spend the afternoon tobogganing.

use: noun

The infinitive phrase is "to spend the afternoon tobogganing".

An infinitive phrase expresses the action in a sentence. They can often function as nouns, adjectives or adverbs. E. g.: To win the approval of her mother-in-law by cooking dinner was Mary's only hope. The infinitive phrase in bold functions as a noun because is the subject of the sentence. When the phrase explains 'how' it functions as and adjective, when the phrase explains 'why' it functions as an adverb.