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Interpretation of complement

Proceeding as before we can read the conditional statement for the complement with the help of two ways arrow as :

x A x U a n d x A

In terms of minus or difference operation,

A = U A

It is clear from the representation on Venn’s diagram that the universal set comprises of two distinct sets – set A and complement set A’.

U = A A

Compliment of universal set

The complement of universal set is empty set. It is so because difference of union set with itself is the empty set (see Venn's diagram).

U = { x : x U a n d x U } = φ

Complement of empty set

The complement of the empty set is universal set. It is so because difference of union set with the empty set is universal set (see Venn's diagram).

φ = { x : x U a n d x φ } = U

Complement of complement set is set itself

The complement of complement set is set itself. The complement set is defined as :

A = U A

Now, complement of complement set is :

A = U A

Let us consider the example, where :

U = { 1,2,3,4,5,6,7,8 }

A = { 1,2,3,4,5,6 }

Then,

A = { 1,2,3,4,5,6,7,8 } - { 1,2,3,4,5,6 } = { 7,8 }

Again taking complement, we have :

A = { 1,2,3,4,5,6,7,8 } - { 7,8 } = { 1,2,3,4,5,6 } = A

Union with complement set

The union of a set with its complement is universal set :

A A = { x : x U a n d x A } { x : x U a n d x A } = U

From Venn’s diagram also, we see that universal set consists of set A and component A’.

U = A A

The two sets on the right side of the equation are disjoint sets. Hence,

A A = U

Intersection with complement set

There is nothing common between set A and its component A’. Thus, intersection of a set with its complement yields the empty set,

A A = φ

De-morgan’s laws

In the real world situation, we want to negate a condition of incidence. For example, consider a class in the school. Some students play either basketball or football or both, but there are students, who play neither basketball nor football. We have to identify later category of students as a set.

Let the set of students playing basketball be “B” and that playing football be “F”. Then, students who do not play basketball is complement set B’ and students who do not play football is complement set F’. We have shown these complement sets separately for visualization. Actually, these complement sets are drawn to the same universal set, "U".

Two complement sets are but overlapping sets. There are students in the set B’ who play football and there are students in the set F’, who play basketball. In order to remove those students playing other game, we intersect two complements. The members of the intersection of two complements, therefore, represent students who play neither basketball nor football. This intersection is shown as third bottom Venn’s diagram in the figure.

Intersection

Intersection of two component sets

Looking at the intersection of two complement sets, however, we observe that this is equal to the complement of union “ B F ”. This conclusion can be derived from basic interpretation as well. We know that union “ B F ” represents students, who play either or both games. The component of the union, therefore, represents, who neither play basketball nor football.

This fact, as a matter of fact, is the first De-morgan’s law. Symbolically,

B F = B F

The second De-morgan’s law is :

B F = B F

In the parlance of illustration given earlier, let us interpret right hand side of the second De-morgan's law. The intersection “ B F ” represents students playing both games. Its complement, therefore, represents students who do not play both games, but may play one of them.

Component set

Component of intersection of two sets

Analytical proof

Here, we shall prove first De-morgan’s law in this section. The second law can be proved in similar fashion. Let us consider an arbitrary element “x” belonging to set ( A B )’.

x A B

x A B

Then, by definition of union,

x { x : x A o r x B }

Here, “not or” is interpreted same as “and”,

x A a n d x B

x A a n d x B

x A B

But, we had started with ( A B )’ and used its definition to show that “x” belongs to another set. It means that the other set consists of the elements of the first set – at the least. Thus,

A B A B

Similarly, we can start with A B and reach the conclusion that :

A B A B

If sets are subsets of each other, then they are equal. Hence,

A B = A B

Example

Problem 1: In the reference of students in a class, the set “B” represents students, who play basketball. The set “F” represents students, who play football. The set “B” and “F” are left and right circles respectively on the Venn's diagram shown below. Identify regions marked 1 to 8 on the Venn’s diagram. Also interpret regions identified by combination U – (6+7).

Sets

Interpreting sets

Solution : The meaning of regions market 1 – 8 are as given hereunder :

1 : B-F : It represents the difference of “B” and “F”. It consists of students, who play basketball, but not football.

2 : F-B : It represents the difference of “F” and “B”. It consists of students, who play football, but not basketball.

3 : B F : It represents the intersection of two sets. It consists of students, who play both basketball and football.

4 : B: It represents the set “B”. It is union of two disjoint sets “B-F” and “ B F ”. It consists of students, who play basketball.

5 : F: It represents the set “F”. It is union of two disjoint sets “F-B” and “ B F ”. It consists of students, who play football.

6 : B∪F: It represents the union set of set “B” and “F”. Equivalently, it is union of three disjoint sets “B-F”, “ B F ” and “F-B”. It consists of students, who play either of two games or both.

7 : ( B F )’: It represents the component of union set “ B F ”. It consists of students, who play neither basketball nor football.

8 : B - F F - B : It represents union of two disjoint difference sets “B-F” and “F-B”. It consists of students, who play only one game.

The region, identified by U – (6+7), is complement of “ B F ”. It represents students, who do not play both games, but may play one of them.

Questions & Answers

how can chip be made from sand
Eke Reply
are nano particles real
Missy Reply
yeah
Joseph
Hello, if I study Physics teacher in bachelor, can I study Nanotechnology in master?
Lale Reply
no can't
Lohitha
where we get a research paper on Nano chemistry....?
Maira Reply
nanopartical of organic/inorganic / physical chemistry , pdf / thesis / review
Ali
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
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Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
hey
Giriraj
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
has a lot of application modern world
Kamaluddeen
yes
narayan
what is variations in raman spectra for nanomaterials
Jyoti Reply
ya I also want to know the raman spectra
Bhagvanji
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
how did you get the value of 2000N.What calculations are needed to arrive at it
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What is power set
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Period of sin^6 3x+ cos^6 3x
Sneha Reply
Period of sin^6 3x+ cos^6 3x
Sneha Reply

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Source:  OpenStax, Functions. OpenStax CNX. Sep 23, 2008 Download for free at http://cnx.org/content/col10464/1.64
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