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}