a. Set H is the set of all prime numbers less than 10.
H = {2, 3, 5, 7}

b. Set J is the set of all composite numbers.
J = {4, 6, 8, 9, 10, 12, ...}

examples

• refers to the number of elements in the set

• it is denoted by n(A) or |A|

n(H) or |H|= 4
n(J) or |J| = ∞

CARDINALITY OF A SET: fINITE SET VS INFINITE SET

let's practice

Set S is a set of odd counting number less than 0.

S = { } or S = ∅

example

• it is possible that a set has no element
  

empty or null set

let's practice

superset

subset

Subset and superSet

let's practice

equivalent set

Two sets that have the same elements.

F = {r, e, a, d}
G = {d, e, a, r}
F = G

equal set

equal and equivalent sets

let's practice

Write all the proper subsets of D = {1, 3, 5}

{1}, {3}, {5}, {1, 3}, {1, 5}, {3, 5}, { }

Example

• is a subset that contains some, but not all, of the elements of the original set

Proper subset