Basic concepts

A set is a collection of stuff, items, things… We’ll call them elements.

We can have a set called A that contains some numbers $ A =\ {1,2,3,9} $ and a set called B than contains names $ A =\ {Daniel, Alfredo, Vikas, Praveen, Bjorn} $ .

We can say that an element is part of a set: $ 3 \in A $ We can also say that 5 is not an element of A: $ 5 \notinA $

We’ll call cardinality to the number of elements in the set. In these cases $ | A | = 4 $ and $ | B | = 5 $

Properties of the sets

The order is not important and listing an element more than once doesn’t change the set.

The empty set

Interception

Union

The cardinality of the union of two sets: