Introduction to Sets in Mathematics

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Questions and Answers

Which of the following is the correct symbol for the union of two sets A and B?

  • A - B
  • A ∪ B (correct)
  • A × B
  • A ∩ B

If B is a subset of A, then A ∪ B = B.

False (B)

What is the name of the property that states A ∪ B = B ∪ A?

Commutative law

The ______ of two sets A and B is represented by the symbol '∩' and includes only elements that are common to both sets.

<p>intersection</p> Signup and view all the answers

Match the following terms to their corresponding definitions:

<p>Union = The set of all elements that are common to both A and B Intersection = The set of all elements that are either in A or in B Subset = A set where all elements are also contained within another set Empty set = A set that contains no elements</p> Signup and view all the answers

Which of the following sets is a subset of A = {1, 2, 3, 4, 5}?

<p>{1, 3, 5} (D)</p> Signup and view all the answers

What is the result of A ∪ φ, where φ represents the empty set?

<p>A</p> Signup and view all the answers

The set {3, 6, 9, 12} can be written in set-builder form as {x : x is a ______ of 3, where x is a natural number}.

<p>multiple</p> Signup and view all the answers

The intersection of two sets can be visualized using a Venn diagram.

<p>True (A)</p> Signup and view all the answers

The set {2, 4, 8, 16, 32} can be represented in set-builder form as {x : x = 2^n, where n is a natural number}.

<p>True (A)</p> Signup and view all the answers

What is the set-builder form of the set {5, 25, 125, 625}?

<p>{x : x = 5^n, where n is a natural number and 1 ≤ n ≤ 4}</p> Signup and view all the answers

Which of the following sets is an infinite set?

<p>{x : x is an odd natural number} (B), {x : x is a multiple of 5} (C)</p> Signup and view all the answers

Match the following sets with their descriptions:

<p>{x : x is an odd natural number} = The set of all odd natural numbers {x : x is an integer, -15 ≤ x &lt; 5} = The set of all integers from -15 to 4 {x : x^2 = 25} = The set containing the square roots of 25 {x : x is an integral positive root of the equation x^2 - 2x - 15 = 0} = The set containing the positive integer solutions to the equation x^2 - 2x - 15 = 0</p> Signup and view all the answers

The set {x : x - 5 = 0} can be written in roster form as {______}

<p>{5}</p> Signup and view all the answers

The sets {x : x^2 = 25} and {x : x is an integral positive root of the equation x^2 - 2x - 15 = 0} are equal.

<p>False (B)</p> Signup and view all the answers

What are the elements of the set {n : n ∈ Z and n^2 ≤ 4}?

<p>{-2, -1, 0, 1, 2}</p> Signup and view all the answers

Who is credited with developing the theory of sets?

<p>Georg Cantor (A)</p> Signup and view all the answers

The concept of sets is only used in the field of mathematics.

<p>False (B)</p> Signup and view all the answers

What is the set of all natural numbers represented as?

<p>N</p> Signup and view all the answers

The set of all ______ numbers is represented by the symbol Q.

<p>rational</p> Signup and view all the answers

Which of the following is NOT an example of a well-defined collection mentioned in the text?

<p>All the happy people in the world (A)</p> Signup and view all the answers

Match the symbols with their corresponding sets:

<p>N = Set of all natural numbers Z = Set of all integers Q = Set of all rational numbers R = Set of all real numbers</p> Signup and view all the answers

What is the set of positive integers represented as?

<p>Z+</p> Signup and view all the answers

The study of geometry, sequences, and probability does not require knowledge of sets.

<p>False (B)</p> Signup and view all the answers

Which of the following represents the set of all natural numbers less than 100 in set-builder form?

<p>{x : x is a natural number and x &lt; 100} (A)</p> Signup and view all the answers

The set {1, 2, 3, 6, 9, 18} is equivalent to the set {x : x is a positive integer and is a divisor of 18}.

<p>True (A)</p> Signup and view all the answers

What is the roster form of the set {x : x is an integer and -3 ≤ x < 7}?

<p>{-3, -2, -1, 0, 1, 2, 3, 4, 5, 6}</p> Signup and view all the answers

The set {0} can be described in set-builder form as {x : x is an integer and x + 1 = ______}.

<p>1</p> Signup and view all the answers

Match the following sets described in roster form with their equivalent set-builder form.

<p>{P, R, I, N, C, A, L} = {x : x is a letter of the word PRINCIPAL} {1, 2, 3, 6, 9, 18} = {x : x is a positive integer and is a divisor of 18} {0} = {x : x is an integer and x + 1 = 1} {3, -3} = {x : x is an integer and x² - 9 = 0}</p> Signup and view all the answers

Which of the following is NOT a set?

<p>A team of eleven best-cricket batsmen of the world (A), The collection of ten most talented writers of India (D)</p> Signup and view all the answers

The symbol '∈' denotes that an element belongs to a set, and '∉' means it does not belong to a set.

<p>True (A)</p> Signup and view all the answers

What is the difference between a set and a collection?

<p>A set is a well-defined collection of distinct objects, while a collection can simply be a group of objects without a strict definition of membership.</p> Signup and view all the answers

What is the union of the sets X = {1, 3, 5} and Y = {1, 2, 3}?

<p>{1, 2, 3, 5} (C)</p> Signup and view all the answers

The sets A - B, A ∩ B, and B - A are always disjoint.

<p>True (A)</p> Signup and view all the answers

Given A = {a, b} and B = {a, b, c}, what is A ∪ B?

<p>{a, b, c}</p> Signup and view all the answers

If A ⊂ B, then A ∪ B = ______.

<p>B</p> Signup and view all the answers

Match the following sets with their correct descriptions:

<p>A - B = The set containing elements of A that are not in B A ∩ B = The set containing elements common to both A and B B - A = The set containing elements of B that are not in A</p> Signup and view all the answers

Which of the following pairs of sets are disjoint? (Select all that apply)

<p>{1, 2, 3, 4} and {x : x is a natural number and 4 ≤ x ≤ 6 } (C), {x : x is an even integer } and {x : x is an odd integer} (D)</p> Signup and view all the answers

What is the difference between the sets A = {3, 6, 9, 12, 15, 18, 21} and B = {4, 8, 12, 16, 20} (A - B)?

<p>{3, 6, 9, 15, 18, 21}</p> Signup and view all the answers

If X = {a, b, c, d} and Y = {f, b, d, g}, then X ∩ Y = ______

<p>{b, d}</p> Signup and view all the answers

Given a universal set U = {1, 2, 3, 4, 5, 6} and a set A = {2, 3}, what is the complement of A, denoted as A'?

<p>{1, 4, 5, 6} (C)</p> Signup and view all the answers

For any sets A and B, the complement of the union of A and B is equal to the intersection of the complements of A and B. This is known as De Morgan's Law.

<p>True (A)</p> Signup and view all the answers

If U represents the universal set and A is a subset of U, what is the result of (A')'?

<p>A</p> Signup and view all the answers

The ______ of two sets is the set containing elements that are in both sets.

<p>intersection</p> Signup and view all the answers

Match the following set operations with their descriptions:

<p>A ∪ B = Union of sets A and B A ∩ B = Intersection of sets A and B A' = Complement of set A (A ∪ B)' = Complement of the union of sets A and B</p> Signup and view all the answers

Given sets A = {1, 2, 3} and B = {2, 4, 5}, what is A ∪ B?

<p>{1, 2, 3, 4, 5} (C)</p> Signup and view all the answers

The complement of the empty set (φ) is equal to the universal set (U).

<p>True (A)</p> Signup and view all the answers

What is the name of the law that states (A ∪ B)' = A' ∩ B'?

<p>De Morgan's Law</p> Signup and view all the answers

Flashcards

Set

A collection of distinct objects considered as a whole in mathematics.

Georg Cantor

German mathematician known for developing set theory.

Natural Numbers

The set of positive integers starting from 1, 2, 3, and so on.

Integers

The set of whole numbers including negative numbers, zero, and positive numbers.

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Rational Numbers

Numbers that can be expressed as a fraction of two integers.

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Real Numbers

All the numbers on the number line, including rationals and irrationals.

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Vowels in English Alphabet

Set of letters a, e, i, o, u that are used in English words.

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Well-defined Collection

A set where it's clear whether an object belongs to it or not.

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Set-builder form

A notation to describe a set by a property that its members satisfy.

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Odd natural numbers

The set of positive integers that are not even, such as 1, 3, 5.

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Equal sets

Two sets are equal if they contain exactly the same elements, regardless of order or repetition.

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Null set

A set that contains no elements, often denoted by {} or ∅.

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Finite sets

Sets that contain a countable number of elements.

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Infinite sets

Sets that contain an uncountable number of elements, extending indefinitely.

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Parallel lines

Lines in a plane that never meet and are at a constant distance apart.

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Set-builder notation

A notation for describing a set by stating its properties. Example: {x : P(x)}.

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Roster form

A way to list all elements of a set explicitly. Example: {1, 2, 3}.

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Divisor

A number that divides another without leaving a remainder. Example: 3 is a divisor of 18.

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Even integers

Integers that are divisible by 2. Example: ..., -4, -2, 0, 2, 4, ... .

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Prime number

A natural number greater than 1 that has no positive divisors other than 1 and itself. Example: 2, 3, 5, 7.

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Match sets

To connect equivalent sets described in different forms. Example: matching roster and set-builder forms.

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Union of Sets

The set of elements in either A or B, or both.

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A ∪ B = A

If B is a subset of A, the union is just A.

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Commutative Law

A ∪ B = B ∪ A; order doesn't matter.

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Associative Law

(A ∪ B) ∪ C = A ∪ (B ∪ C); grouping doesn’t matter.

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Identity Element of Union

A ∪ φ = A; union with empty set gives A.

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Idempotent Law

A ∪ A = A; merging a set with itself yields the same set.

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Intersection of Sets

The set of elements common to both A and B, denoted A ∩ B.

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A ∩ B = B

If B is a subset of A, the intersection is B.

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Mutually disjoint sets

Sets that have no elements in common, resulting in an intersection of the null set.

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Subset

Set A is a subset of set B if every element of A is also in B.

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Disjoint sets example

Sets that do not share any elements, like even and odd integers.

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Set difference

The difference A - B consists of elements in A that are not in B.

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Natural number set

The set of positive integers starting from 1, 2, 3, and so on.

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Empty set

A set with no elements, denoted by φ or {}.

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Complement of a set

The elements not in the set within a universal set U.

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De Morgan's Laws

Rules describing the relationship between complements and unions/intersections of sets.

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Complement of union

For any sets A and B, (A ∪ B)' = A' ∩ B'.

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Complement of intersection

For any sets A and B, (A ∩ B)' = A' ∪ B'.

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Double complement law

The complement of the complement of A equals A: (A')' = A.

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Complement laws

Special rules: A ∪ A' = U and A ∩ A' = ∅ (empty set).

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Empty set complement

The complement of the empty set is the universal set: ∅' = U.

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Universal set

The set that contains all possible elements under consideration.

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Study Notes

Sets

  • Sets are fundamental in modern mathematics
  • Used in various branches of mathematics, including geometry, sequences, and probability
  • Developed by Georg Cantor (1845-1918)
  • Often represent collections of objects with specific characteristics

Sets and Their Representations

  • Everyday collections, like card packs, teams, or numbers, correspond to sets in mathematics.
  • Examples of well-defined collections include: odd natural numbers under 10, vowels in the English alphabet, prime factors of 210, and solutions to a quadratic equation.
  • Sets can be in roster form (listing elements within braces), or set-builder form (describing a property that elements must satisfy).
  • Roster format lists elements separately
  • Set-builder lists a general rule for defining elements
  • The order of elements in a roster set is not important
  • The same element isn't listed more than once in a set

Special Sets

  • N: Natural Numbers (1,2,3...)
  • Z: Integers (-∞, ∞)
  • Q: Rational Numbers
  • R: Real Numbers
  • Z+: Positive Integers (1, 2, 3...)
  • Q+: Positive Rational Numbers
  • R+: Positive Real Numbers

Well-Defined Collections

  • A well-defined set is one where it's clear whether a given object belongs to the collection
  • A collection of five most renowned mathematicians is not well-defined, because the criterion for being the most renowned is not universally agreed upon.

Objects, Elements, and Members

  • Objects, elements, and members of a set are interchangeable
  • Sets are denoted by capital letters (A, B, C)
  • Elements are denoted by lowercase letters (a, b, c)
  • The Greek symbol ∈ means "belongs to"
  • If 'a' belongs to A, it's written as a ∈ A
  • If 'b' does not belong to A, it's written as b ∉ A

Finite and Infinite Sets

  • A set is finite if it has a specific (countable) number of elements
  • Set A (e.g., {1, 2, 3, 4, 5}), contains 5 elements and is finite. Set B (e.g., {all natural numbers}), is infinite
  • A set is infinite if the number of elements is not finite. For example the set of all natural numbers

Equal Sets

  • Sets are equal if they have the same elements, regardless of order or repetition
  • Example: {1, 2, 3} and {3, 1, 2} are equal sets

Subsets

  • A set A is a subset of set B (A ⊂ B) if every element of A is also in B
  • The empty set (Ф) is considered a subset of every set.
  • For example: {1, 2} ⊂ {1, 2, 3} and {1, 3} ⊂ { 1, 2, 3 }

Operations on Sets

  • Union: The union of sets A and B (A ∪ B) is the set containing all elements in either A or B (or both)
  • Intersection: The intersection of sets A and B (A ∩ B) is the set containing only the elements present in both A and B
  • Difference: The difference of sets A and B (A – B) is the set containing elements present in A but not in B

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