
# 10: Some Prerequisite Topics


The topics presented in this section are important concepts in mathematics and therefore should be examined.

• 10.1: Sets and Set Notation
A set is a collection of things called elements. For example {1,2,3,8} would be a set consisting of the elements 1,2,3, and 8. To indicate that 3 is an element of {1,2,3,8}, it is customary to write 3∈{1,2,3,8}. We can also indicate when an element is not in a set, by writing 9∉{1,2,3,8} which says that 9 is not an element of {1,2,3,8}. Sometimes a rule specifies a set.
• 10.2: Well Ordering and Induction