For reflexive, symmetric and transitive relations. Use it with the tag (relations).

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Give an example of a relation R on $A^2$ which is reflexive, symmetric, and not transitive

I am just looking for some clarification on this exercise: Let $A = \{a,b,c,d\}$. Give an example of a relation $R$ on $A^2$ which is reflexive, symmetric, and not transitive. I understand that if I ...
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64 views

How to find the Equivalence class for a given set?

I'm really having trouble understanding these equivalence classes. Could someone please guide me through the following problem step by step, and help explain this. I have a final exam next week, and ...
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42 views

Equivalence Class.

Let R be the relation of congruence mod 4 on Z: a R b if a - b = 4k, for some k in Z. What integers are in the equivalence class of 31? How many distinct equivalence classes are there? What are ...
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list all the equivalence relation [duplicate]

list all the equivanlance relations in the set A={1,2,3,4) so there should be 15 right? so what I got so far (1 1) (22) (33) (44) (12) (13) (14) (21) (23) (24) (31) (32) (34) (41) (42) (43) these ...
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56 views

Reflexivity of the relation between strings over language $L$ defined by $xc \equiv L$ and $yc \equiv L $

Given any two strings, call them $x$ and $y$, over any language $L$ and given property such that if $xc \equiv L$ and $yc \equiv L $ (where $c$ is some string), then $x \equiv y$. I would ...
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66 views

Prove that if the relation (R) is symmetric and antisymmetric on the set X, there exists a Y subset of X such that R is the = relation on Y.

Prove that for any relation R on a set X that is both symmetric and antisymmetric, there is subset Y \subseteq X for which R is the relation = on Y. I will tell you what I know. I know that ...
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Power Set, Bijection Function, Equivalence Relation

Let $S$ be a set and $P(S)$ the power set of $S$. For sets $A,B⊆P(S)$, we say that $A \sim B$ if there exists a bijective function $f: A \rightarrow B$. Show that $\sim $ is an equivalence relation.
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Show that $R \cap R^*$ and $R \cup R^*$ are equivalence relations.

Let $R$ be a reflexive and transitive relation on a set $S$. Let $R^*$ be the dual relation, $(a,b) \in R^*$ if and only if $(b,a) \in R$. Show that $R \cap R^*$ and $R \cup R^*$ are equivalence ...
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53 views

How to prove that equality is an equivalence relation?

Probably, it's a elementary question, but I would like some explanation. Everyone knows that equality relation is (i) reflexive, (ii) symmetric and (iii) transitive, that is, satisfies (i) $x=x$; ...
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On $N \times N $ define the relation R, setting $(a,b),(c,d) \in R$ if and only if $a+d=b+c$. Show that $R$ is an equivalence relation.

On $N \times N $ define the relation R, setting $(a,b),(c,d) \in R$ if and only if $a+d=b+c$ a. Show that $R$ is an equivalence relation. My attempt: By definition 6.2.3 $R$ is an equivalence ...
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38 views

Show that the equivalence classes of $\sim$ are left cosets of $H$ in $G$.

Let $H \leq G$ and define a relation on $G$ by $x \sim y$ if $y^{-1}x \in H$. Show that $\sim$ is an equivalence relation on $G$ and then show that the equivalence classes of $\sim$ are left cosets ...
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1answer
41 views

Equivalence relation: prove that $(X \cap Y) $\ $E $ $\subset (X$ \ $E) \cap (Y$ \ $E)$

I need to prove that $(X \cap Y) $\ $E $ $\subset (X$ \ $E) \cap (Y$ \ $E)$, where $E$ is an equivalence relation over $A$ and $X,Y \subset A$. I don't know where to begin. I know that $X$ \ $ E$ ...
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26 views

What does a null relation on all real numbers look like?

I'm being asked to test for reflexivity, symmetry, transitivity, and antisymmetry on a null relation for all real numbers, i.e. $X=\mathbb{R}; R = \emptyset $. What would such a resulting set look ...
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1answer
19 views

Determining equivalence classes on $\Bbb{R}$.

Say we have the following equivalence relation on $\Bbb{R}$: $$a\sim b\iff a-b\in\Bbb{Q}$$ What do the equivalence classes look like? On a preliminary investigation I got the following equivalence ...
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26 views

Proving that if $E, F$ are equivalence relations on $A$ and $E \subseteq F$, then there is a surjection from $A\setminus E$ to $A\setminus F$

Proving that if $E, F$ are equivalence relations on $A$ and $E \subseteq F$, then there is a surjective function from $A\setminus E$ onto $A\setminus F$. What does $E \subseteq F$ even mean? Does it ...
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33 views

Proof of equivalence relation on set.

I'm new to the whole relations topic and stumbled upon a problem. I know that an equivalence relation is a relation that is symmetric, transitive, reflexive, (and not usually anti-symmetric). But ...
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54 views

theorems on equivalence classes

I have a few short proofs that I wish to be checked regarding equivalent classes. Suppose that R is an equivalence relation on set X. If $a, b \in X$, then $a\in [a]$ $[a] = [b] \iff (a, b) \in R$ ...
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1answer
56 views

Equivalence Relation on R (real numbers)

Let R be the relation on R(real numbers) defined by: For all x, y (that belong) to R(real numbers), x relates y <=> x-y (that belongs) to Z. (a) Is R an equivalence relation? Prove your answer. ...
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74 views

Describing Equivalence Classes using set builder notation

How would you describe all the equivalence classes for the relation: $congruence$ $modulo$ $5$ over $Z$, using set builder notation?
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Size of partitions

I am looking at a problem and really confused. Let $X$ be a set and $R$ a subset of $ X×X $. We write $x1 ∼ x2$ if and only if $(x1, x2) ∈ R$ Suppose now that $R$ defines an equivalence relation and ...
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39 views

How to show properties of a given relation?

I am given that R is a relation on the given set X, and I have to show if the relation is (i) reflexive, (ii) symmetric, (iii) transitive, (iv) asymmetric, and (v) give an example of an element of ...
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71 views

Show that if $R$ is a strict partial order on $X$, and $R$ is not linear, then there exists a strict partial order $R'$ and $R' \supsetneqq R$.

Question: Show that if $R$ is a strict partial order on $X$, and $R$ is not linear, then there exists a strict partial order $R'$ and $R' \supsetneqq R$. My attempt: By definition 6.23,6.3.1, and ...
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115 views

An empty relation on a non-empty set — can it be an equivalence relation?

Given a non-empty set, A, and an empty relation, R, on that set A, can it be the case that the relation R is an equivalence class? Transitivity. (a,b) in R, (b,c) in R ===> (c,a) in R. This is ...
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29 views

How to determine a equivanelce relation?

I have a problem to understand the following output: Determine "representative system" or a "system of representatives" :).....for the following equivalence relation ...
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35 views

Sets equivalence relations

I seem to be having a hard time understanding some basic sets concepts. In week 5 of my class, I learnt about the cross product of 2 sets to be the following $A \times B = \{(a,b) : a \in A, b \in B ...
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26 views

A proper term for equivalence relation with a finite quotient set

Is there a proper term for an equivalence relation $\sim$ on some set $M$ such that it partitions $M$ into finitely many equivalence classes? Finite equivalence relation? or co-finite? or equivalence ...
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33 views

Equivalence Set, Subsets

Just a quick question: If a = [A] and a belongs to N (set of all natural numbers) doesn't that mean that A is a subset of N? The reason I'm asking this is because I'm trying to prove the theorem ...
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1answer
141 views

I don't understand equivalence relations

I'm trying to show that the left coset with a subgroup is an equivalence relation. So taking some element $g \in G$ and a subgroup $H$, the left coset is defined as $gH = \{gh : h \in H\}$. That means ...
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Determining Equivalence Relation on $\Bbb{Z}$

Alright, I have a homework problem which I have researched, read up on and I (think) solved. I just need someone to either confirm my answer (and re-affirm my knowledge) or explain why I am wrong. ...
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1answer
91 views

Determine if R is an equivalence relation

I've got this question: Consider the relationship $R$ between ordered pairs of natural numbers such that $(a, b)$ is related to $(c, d)$ (denoted by $(a, b) R (c, d)$) if and only if $ad = bc$. ...
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104 views

About Kernel and the coimage of a function

Introduction I was serching for a concept of "equivalence relations" induced by an arbitrary function in a "natural" way and I found the concept of Kernel. But I'm not sure that I understand it and ...
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Prove congruence relation.

Let $\sim$ be a relation where $x \sim y \Leftrightarrow x = y \lor (x \in I \land y \in I)$. Show $\sim$ is a congruence relation on $S$ where $S= \{a,b, c, d, e\}$ and $I = \{a, d\}$. One of the ...
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Prove transitivity of relation.

Let $\sim$ be a relation where $x \sim y \Leftrightarrow x = y \lor (x \in I \land y \in I)$. Show $\sim$ is a congruence relation on $S$ where $S= \{a,b, c, d, e\}$ and $I = \{a, d\}$. One of the ...
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Is $x \sim y \Leftrightarrow x,y$ are even an Equivalence relation?

The following instruction defineds an Equivalence relation on the set of natural numbers. $x \sim y \Leftrightarrow x,y$ are even My idea: Reflexivity: $x \sim x \Leftrightarrow x,x$ is even ...
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1answer
66 views

Number of Equivalence relations of $\{1,2,3\}$

Let $M$ be the set $\{1,2,3\}$. How many Equivalence relations $R \subset M \times M$ exists? My idea is to count the disjoint partitions of M: $K_1= ...
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60 views

$R$ is transitive if and only if $ R \circ R \subseteq R$

Question: Let $R$ be a relation on a set $S$. Prove the following. $R$ is transitive if and only if $ R \circ R \subseteq R$. Definition 6.3.9 states that we let $R_1$ and $R_2$ be relations on a ...
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36 views

Let $x\in \mathbb{R}$ and $z\in\mathbb{C}$. And define equality ($x=z$) iff $x=(0,x)$. Is this equality well defined?

Let $x\in \mathbb{R}$ and $z\in\mathbb{C}$. And define equality ($x=z$) iff $x=(0,x)$. Is this equality well defined ? Okay. It is easily shown that something goes wrong if you define equality in ...
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68 views

Is $a \sim b$ such that $\gcd(a,b) > 1$ an equivalence relation?

Is $a \sim b$ such that $\gcd(a,b) > 1$ an equivalence relation? I know that it's reflexive, since $\gcd(a,a) > 1$. It's also symmetric since $\gcd(a,b) > 1$ iff $\gcd(b,a) > 1$. ...
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Equivalence Relation on $\mathbb{R}$ and its partition $\mathbb{R}/\sim$

Define the equivalence relation $\sim$ on $\mathbb{R}$ as follows: $$\forall a,b\in\mathbb{R},\ a\sim b\ \Leftrightarrow\ b-a\in\mathbb{Z}$$ I can prove that this is an equivalence relation, but I ...
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Question about Equivalence relation and partition

This is my first time of Abstract algebra, and I don't know how to solve this problem. Although I have an idea to solve this problem, I can't assure whather it is correct or not. Please show me how ...
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The closures of a binary relation

I have the following dilemma concerning the equivalence closure of a binary relation. Let $X$ be a nonempty set and $R\subseteq X\times X$ (i.e., a binary relation over $X$). Consider the following ...
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Let ~ be an equivalence relation on a set S. Show that b is an element of cl(a) <=> cl(a) = cl(b) (Where all a,b are elements of S)

This was a question on my last equivalence relations quiz and I'm not yet comfortable with the whole "class" idea. I understand that I must show transitivity, reflexivity and symmetry however I'm not ...
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221 views

Determine the number of equivalence relations on the set {1, 2, 3, 4}

Hi this was a question listed on my last proofs and conjectures midterm. It is similar to my previous post however this asks a different question which is throwing me off.. Do I simply list all ...
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54 views

Determining whether relations are equivalence classes, and finding the equivalence classes

Determine if each of the following relations is an equivalence relation. If so, determine the equivalence classes. $S = \Bbb Z$, $a \sim b \iff a \equiv b \pmod 3$ or $a \equiv b \pmod 5$. ...
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Show that the relation in set of real number is an equivalence [closed]

Show that the relation $R = \{(a ,b)|a^2 = b^2\}$ in the set of real numbers is an equivalence relation.
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Equivalence relation and quotient set

I'm studying for a test and got stuck in one question regarding equivalence relations and quotient set. Here is the question: Let $F=\mathbb{R}\to \mathbb{R}$ be the set of functions from ...
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25 views

Checking the equivalence relations of sets

$S=\{0,1,2,3\}, R:SxS, (m,n)\in R \text{ if } m+n=4$. From the condition of $R$, I found that $R=\{(2,2),(1,3),(3,1)\}$. Now I have to see if $R$ is reflexive, symmetric, antisymmetric, and ...
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64 views

Let $H=\{2^m: m ∈ Z\}$ Where $m$ is any integer, and $ a\sim b\Leftrightarrow a/b $ is an element of $H$.

Show that is an equivalence relation and describe the elements in the equivalence class $\operatorname{cl}(3)$. We're studying sets and equivalence in my mathematical proofs class. As this is a ...
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40 views

Counting Ordered Pairs

Let $A$ be a finite set with $n \geq 4$ elements and let $\rho$ be an equivalence relation on $A$. Suppose that there are exactly $4$ equivalence classes, $C_1$, $C_2$, $C_3$, $C_4$. Moreover we know ...
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35 views

Equivalence Relation determined by $f(x)=x^2$

I have an exercise from my professor; For the function $f(x)=x^2$, for all $x\in \mathbb{R}$, describe the equivalence relation determined by $f$. So we are working in the set $\mathbb{R}$, so ...