1. BLACKBOX
TAF 3023:
MATHEMATICS DISCRET
TASK 2:CONCEPT OF SET
2. DEFINITIONS OF SETS
• A set is any well-defined collection of
objects
• The elements or members of a set are the
objects contained in the set
• Well-defined means that it is possible to
decide if a given object belongs to the
collection or not.
3. 1)WAY OF LISTING THE ELEMENTS
OF SETS
A. Roster Method
-listing the elements in any order and enclosing
them with braces.
Example:
A= {January, February, March…December}
B={1,3,5…}
4. B. Set builder notation
-giving a descriptive phrase that will clearly identify
the elements of the set.
Example:
{ x Є A| P(x) }
5. 2)BASIC PROPERTIES OF SETS
sets are inherently unordered
-no matter what a,b, and c denoted
{a,b,c}={a,c,b}={b,a,c}=
{b,c,a}={c,a,b}={c,b,a}
All element are unequal
-if a=b then {a,b,c}={a,c}=
{b,c}={a,a,b,a,b,c,c,c,c}
-this sets contains at most 2 elements
-number of occurence are not important)
6. 3)SET MEMBERSHIP
• ϵ-- “is an element of”(note that it is a shape like
“E” as in an element).
• ∉-- “is not an element of”.
• Example:-If A={4,7,5,8}, then 4 ϵ A, but 2 ∉ A.
4)EMPTY SET
• ᴓ is the label for empty set.
• Example:- ᴓ ={ }
7. 5)SET OF NUMBER
• In term of capital alphabet to show the specific
set of number.
• Example:
1) natural number, N= { x:x = 1,2,3….}
2) Integer, Z = {x:x = …-2,-1,0,1,2}
3) Rational number, Q { x:x = is a rational
number}
4)Irrational number, R { x:x = irrational number}
8. 6)SET OF EQUALITY
• Set which has same or equal element in term on
it’s declaration in the content.
• Note that set have a same element
• In some of case, it does not matter if the
arrangement is correct order or not
How to understand
( if the set is equal)
• Let’s assume that set P is defined same set of Q.
• So, if the set have same element and although
not in correct order it can be considered the both
set is equal.
9. How to understand
(if it is not equal)
• If the set P does not have same element with set
Q , so it is not equal.
• Eventhough the least one element either set P or
set Q not in both set, it consider as not equal
laaa…
• Example :
P = {a, b, c, d}
Q = {d, c, b, a}
P=Q
each elements of set P that is a, b, c, d is same
with element of set Q that is 8, 4, 2, 6. rearrange
the elements of the set it still be same.
10. 7)VENN DIAGRAM
also known as set diagram. which known as a diagram indicates all of the
possible logical relations between sets of finite collection (aggregation).
Venn diagrams are alternatives to solve problems in market research, in
science, in social science, etc.
where often overlapping information is obtained and needs to be organized.
history facts on Venn Diagram:
the Venn Diagram were formulated by John Venn on 1880. Nowadays, The
Venn Diagram can be use to illustrate simple set relationship in probability,
logic, statistics, linguistics, and computer science.
11. examples
1. From a survey of 100 workers, a marketing
research company found that 75 workers owned
stereos, 45 owned cars, and 35 owned cars and
stereos.
a) How many students owned either a car or a stereo?
b) How many students did not own either a car or a stereo?
12. METHOD?
a) Start with a Venn Diagram and label the different categories:
b) Fills the number of workers who own both cars and stereos, resulting in the intersection of
the two sets:
c)Fills the remaining numbers for the both 2 sets. So, the total of 45 workers own cars, and 35
have already been listed, then 45 - 35 = 10 workers own cars only.
Same goes to the 75 workers own stereos and 35 point out.
Thus, 75 - 35 = 40 workers who own stereos only:
13. answers!
therefore, after some footages on the diagrams drawn. We are
able to solve the questions!
a) How many workers have either a car or a stereo?
The question asks either or which is union of the sets.
From what we able to gain from the diagram, the number of elements
in A = 10 + 35
and the number of elements in B which are NOT in A (different area)
are 40.
So the union would be 10 + 35 + 40 = 85
b) How many workers did not have either a car or a stereo?
The question asks for the number not in either A nor B
(namely, the complement of A B or (A B)' ).
Since there are 100 workers assumed, then the total is obtained
by subtracting those who own either a car or stereo from the total
number of workers surveyed
in such expression:
100 - 85 = 15.
14. 8)SUBSET
• Set A is a subset of set B if and only if every element in
A is also in B.
• Example : We have the set {1, 2, 3, 4, 5}. A subset of
this is {1, 2, 3}. Another subset is {3, 4} or even
another, {1}. However, {1, 6} is not a subset, since it
contains an element (6) which is not in the parent set
• NOTATION : When we say that A is a subset of B, we
write A B. Or we can say that A is not a subset of B
by A B ("A is not a subset of B")
15. Example: Let A be multiples of 4 and B be
multiples of 2. Is A a subset of B? And is B a
subset of A?
By pairing off members of the two sets, we can see
that every member of A is also a member of B, but
not every member of B is a member of A:
•So, A is a subset of B, but B is not a subset of A.
16. Proper Subsets
•A is a proper subset of B if and only if every
element in A is also in B, and there exists at least
one element in B that is not in A.
•Example: {1, 2, 3} is a subset of {1, 2, 3}, but is
not a proper subset of {1, 2, 3}.
•Example: {1, 2, 3} is a proper subset of {1, 2, 3,
4} because the element 4 is not in the first set.
•You should notice that if A is a proper subset of B,
then it is also a subset of B.
19. 10)SET OPERATION
A)UNION
union of the sets A and B, denoted by A ∪ B
elements that are either in A or in B, or in both.
A ∪ B = {x | x ∈ A ∨ x ∈ B}.
B)INTERSECTION
• intersection of the sets A and B, denoted by A ∩
B
• set
• containing those elements in both A and B
A ∩ B = {x | x ∈ A ∧ x ∈ B}.
20. C)DISJOINT SET
• Two sets are called disjoint if their intersection is
the empty set.
• Meaning that two sets has nothing in common
D)SET DIFFERENCE
• Definition
• The (set) difference between two se
ts S and T is written S∖T, and means the set
that consists of the elements of S which are not
elements of T:
• x∈S∖T⟺x∈S∧x∉T
It can also be defined as:
• S∖T={x∈S:x∉T}
• S∖T={x:x∈S∧x∉T}
21. • Illustration by Venn Diagram
The red area in the following Venn diagram illustrates S∖T:
• Example
For example, if S={1,2,3} and T={2,3,4}, then S∖T={1}, while T∖S={4}.
It can immediately be seen that S∖T is not commutative, in general
(and in fact, that it is anticommuntative).
22. E)SET COMPLEMENTARY
So far, we have considered operations in which two sets combine to
form a third: binary operations. Now we look at
a unary operation - one that involves just one set.
The set of elements that are not in a set A is called
the complement of A. It is written A′ (or sometimes AC, or ).
Clearly, this is the set of elements that answer 'No' to the
question Are you in A?.
For example, if U = N and A = {odd numbers}, then A′ = {even
numbers}.
26. 11)GENERALISED UNION AND INTERSECTION
• Union
• A ∪ B ∪ C contains those elements that are in at least
one of the sets A, B, and C
• parentheses do not use to indicate which operation
comes first
• A ∪ (B ∪ C) = (A ∪ B) ∪ C
27. • Intersection
• A ∩ B ∩ C contains those elements that are in
all of A, B, and C
• parentheses also do not use to indicate which
operation comes first
• A ∩ (B ∩ C) = (A ∩ B) ∩ C
28. • Example:
• Let A = {0, 2, 4, 6, 8}, B = {0, 1, 3, 5, 7} and C = {0, 1, 2, 3}. What
are A ∪ B ∪ C and A ∩ B ∩ C ?
• Solution:
The set A ∪ B ∪ C contains those elements in at least one of A,
B, and C.
• A ∪ B ∪ C = {0, 1, 2, 3, 4, 5, 6, 7}
The set A ∩ B ∩ C contains those elements in all three of A, B,
and C.
• A ∩ B ∩ C = {0}
29. • Generalized Union
• The union of a collection of sets is the set that contains those elements
that are members of at least one set in the collection.
• Using notation:
to donate the union of the sets A₁, A₂, . . . , An.
• Generalized Intersection
• The intersection of a collection of sets is the set that contains those
elements that are members of all the sets in the collection.
• Using notation:
• to denote the intersection of the sets A₁, A₂, . . . , An.
