Set Operations - University of New Mexico
Download
Report
Transcript Set Operations - University of New Mexico
Set Operations
Chapter 2 Sec 3
Union
What
does the word mean to
you?
What
does it mean in
mathematics?
Definition
The
union of sets A and B,
written A B , is the set of
elements that are members of
either A or B(or both).
Using set-builder notation,
A B {x:x is a member of A or
x is a member of B}.
The
union of more than
two sets is the set of all
elements belonging to at
least one of the sets.
Example
Find
the union of the following
pair of sets.
◦ A={1,3,5,8,9} and B={2,4,6,7,8,}
Solution
A B
The
= {1,2,3,4,…,9}
solution in the final answer
we list the elements in order and
did not list duplicate elements
because doing so does not affect
set equality.
Intersection
The
essential idea of intersection
is a region that is common to
both sets.
Definition
The
intersection of sets A and B,
written A B , is the set of
elements common to both A and
B.
Using set-builder notation,
A B ={x:x is a member of A and
x is a member of B}.
The
intersection of more than
two sets is the set of elements
that belong to each of the sets.
If A B = , then we say that A
and B are disjoint.
To help us understand we will use
the Venn Diagram
r2
r1
r3
r4
A B
r2 r3
r4
Inside the 2 circles are shaded.
A B
r2
r3
r4
Which region would be shaded?
Complement
If A is a subset of the universal set U, the
complement of A is the set of elements of
U that are not elements of A. This set is
denoted by A’.
Using set builder notation,
A' {x : x U ; x A}
Venn diagram: Complement
r1
r2
What would be the complement?
Example
Find the complement of each set.
◦ U ={1,2,3,…10} and A ={2,4,6,8}
A’ = {1,3,5,7,9}
◦ U is the set of cards in a standard
52 card deck, and F is the set of
face cards.
F’ is the set of nonface cards.
Set difference
The
difference of sets B and A is
the set of elements that are in B
but not in A. This set is denoted
by B-A.
Using set builder notation,
◦ B-A = {x:x is a member of B and x
is not a member of A}.
Venn for set difference, B-A
A
r2
B
r3
r4
Which region would be shaded?
Examples of Set difference.
Find
the set difference.
◦ Find {3, 6, 9, 12}-{x:x is an even
integer}
◦ Therefore we will remove all
the even integers to get {3, 9}