# Theory of proveit.logic.sets.functions¶

Provide description here.

In [1]:
import proveit
%theory # toggles between interactive and static modes


### Local content of this theory

common expressions axioms theorems demonstrations

### Sub-theories

images An image is a set obtained from applying a function to the elements of another set. An injection is a 1-to-1 function. Distinct elements map distinctly. A surjection is an onto function. Its image covers the codomain. A bijection is a 1-to-1 and onto function.