This presentation gives theoretical knowledge of Chapter-1 Sets of Class XI of Maths NCERT Textbook.

1. SETS

2. Introduction
 Why Sets?...
 Notations to be used:
N : the set of all natural numbers
Z : the set of all integers
Q : the set of all rational numbers
R : the set of real numbers
Z+ : the set of positive integers
Q+ : the set of positive rational numbers, and
R+ : the set of positive real numbers.

3. • SET: A well defined collection of objects
Ex: Rivers of India is a well defined collection,
however, the most famous cricketers is not a well
defined collection as it may vary for person to
person.
• Objects of a set are known as elements or
members of a set.
• Sets are usually represented as capital letters and
their elements as small letters.
• So, if A is a set and x is an element of A, we then
write x∈A, and if x is not a member of A, then x∈A

4. Representation
• There are two methods of representing a set:
1. Roaster or Tabular Form
2. Set Builder Form
• In roster form, all the elements of a set are listed, the elements are being
separated by commas and are enclosed within braces { }. For example, the
set of all even positive integers less than 7 is described in roster form as {2,
4, 6}. Order of elements has no relevance in this form.
• In set-builder form, all the elements of a set possess a single common
property which is not possessed by any element outside the set. For
example, in the set {a, e, i, o, u}, all the elements possess a common
property, namely, each of them is a vowel in the English alphabet, and no
other letter possess this property. Denoting this set by V, we write V = {x : x
is a vowel in English alphabet}. The above description of the set V is read as
“the set of all x such that x is a vowel of the English alphabet”. In this
description the braces stand for “the set of all”, the colon stands for “such
that”.

5. Types of Sets
1) Singleton Set
2) Empty Set (Φ or {})
3) Finite Set
4) Infinite Set
5) Universal Set

6. Equal Sets
• Given two sets A and B, if every element of A is also an
element of B and if every element of B is also an element of
A, then the sets A and B are said to be equal.
• Also, the two sets have exactly the same elements.
• Ex: Let A be the set of prime numbers less than 6 and P the
set of prime factors of 30. Then A and P are equal, since 2, 3
and 5 are the only prime factors of 30 and also these are less
than 6.
• A set does not change if one or more elements of the set are
repeated.
• For example, the sets A = {1, 2, 3} and B = {2, 2, 1, 3, 3} are
equal, since each element of A is in B and vice-versa. That is
why we generally do not repeat any element in describing a
set.

7. Subsets, Supersets, Proper Subsets &
Comparable Sets
• Refer Google Jamboard

8. Intervals as Subsets of R
• Let a, b Î R and a < b. Then the set of real numbers { y : a < y < b} is
called an open interval and is denoted by (a, b). All the points
between a and b belong to the open interval (a, b) but a, b
themselves do not belong to this interval.
• The interval which contains the end points also is called closed
interval and is denoted by [ a, b ]. Thus [ a, b ] = {x : a £ x £ b}
• We can also have intervals closed at one end and open at the other,
i.e.,
1) [ a, b ) = {x : a £ x < b} is an open interval from a to b, including a
but excluding b.
2) ( a, b ] = { x : a < x £ b } is an open interval from a to b including b
but excluding a.
• These notations provide an alternative way of designating the
subsets of set of real numbers.

9. Power Set
• The collection of all subsets of a set A is called
the power set of A. It is denoted by P(A). In
P(A), every element is a set.
• Thus, as in above, if A = { 1, 2 }, then
P( A ) = { f,{ 1 }, { 2 }, { 1,2 }}
• In general, if A is a set with n(A) = m, then
n [ P(A)] = 2m.

10. Venn Diagrams
• Most of the relationships between sets can be
represented by means of diagrams which are
known as Venn diagrams. These diagrams
consist of rectangles and closed curves usually
circles. The universal set is represented usually
by a rectangle and its subsets by circles. In
Venn diagrams, the elements of the sets are
written in their respective circles

11. • Ex: Consider U = {1,2,3, ..., 10} a universal set
of which A = {2,4,6,8,10} is a subset. Then the
Venn Diagram for it would be

12. Union of Sets
• Refer Google Jamboard
• Venn Diagram for union of sets is as:

13. Properties of Union
• Refer Google Jamboard

14. Intersection of Sets
• Refer Google Jamboard
• Venn Diagram for intersection of sets is as:

15. Properties of Intersection
• Refer Google Jamboard

16. Difference of Sets
• Refer Google Jamboard
• Venn Diagram for difference of sets is:
• The sets A – B, A ∩ B and B – A are mutually
disjoint sets.

17. Complement of Set
• Refer Google Jamboard

18. Properties of Complement
• Refer Google Jamboard

19. Applications of Union and Intersection
• Refer Google Jamboard