Elements Of a Set

Basic Concept

Elements Of a Set

An element is a member of a set

Notation:

∈  means “is an element of”

∉  means “is not element of”

 

Example:

A = {positive integers between −3 and 3}

 

A = {1, 2}

1 ∈ A  {1 is an element of A}

2 ∈ A  {2 is an element of A}

3 ∉ A {3 is not element of A}

 

Cardinality

The cardinality of a set states the number of elements a set contains

The cardinality is expressed as n(A)

 

Example:

A = {days of the week}

 

A = {sunday, monday, tuesday, wednesday, thursday, friday, saturday}

n(A) = 7 {The number of elements of set A is 7}

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