Sets

Question	Answer
A set is a collection of well-defined objects. The objects in the set are called elements.	The cardinal number of a set A is the number of elements and is denoted by #A or \| A \| .
If a set has no elements, then it is called the null set it the empty set. It Is denoted by the symbol ø or { } .	Two sets are equal if they each have the same elements.
If all the elements of a set A are also in a set B, then we say that A is a subset of B..	If A is a subset of B and A contains all of the elements of B, then A is an improper subset of B. If A is a subset of B but A does not contain all the elements of B then A is a proper subset of B. The null set and the set A itself are both subsets of A.
The universal set is the set that contains all elements. Every set is a subset of the universal set.	The union of two sets is the set of elements contained in either set.
The intersection

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	Created by Fergus Earley almost 8 years ago