Relations

Define three equivalence relations on the set of buildings on a college campus. Determine the equivalence classes for each of these equivalence relations. 

First, let’s take a look at the relevant definitions that we need to know to solve this exercise. Definition: “A relation on a set A is called an equivalence relation if it is reflexive, symmetric, and transitive.” Definition: “A relation R on a set A is called reflexive if (a,a) ∈ R for every element […]

Define three equivalence relations on the set of buildings on a college campus. Determine the equivalence classes for each of these equivalence relations.  Read More »

Which of these relations on the set of all functions from Z to Z are equivalence relations? Determine the properties of an equivalence relation that the others lack

Below are the relevant definitions that we need to know to solve this exercise. Definition: “A relation on a set A is called an equivalence relation if it is reflexive, symmetric, and transitive.” Definition: “A relation R on a set A is called reflexive if (a,a) ∈ R for every element a ∈ A.” Definition:

Which of these relations on the set of all functions from Z to Z are equivalence relations? Determine the properties of an equivalence relation that the others lack Read More »

Which of these relations on the set of all people are equivalence relations? Determine the properties of an equivalence relation that the others lack

Let’s start with the relevant definitions that will help us to solve this exercise. Definition: “A relation on a set A is called an equivalence relation if it is reflexive, symmetric, and transitive.” Definition: “A relation R on a set A is called reflexive if (a,a) ∈ R for every element a ∈ A.” Definition:

Which of these relations on the set of all people are equivalence relations? Determine the properties of an equivalence relation that the others lack Read More »

Let R be the relation on the set of ordered pairs of positive integers such that ((a, b), (c, d)) ∈ R if and only if a + d = b + c. Show that R is an equivalence relation

As usual for us, we will start refreshing the relevant definitions to solve this exercise. Definition: “A relation on a set A is called an equivalence relation if it is reflexive, symmetric, and transitive.” Definition: “A relation R on a set A is called reflexive if (a,a) ∈ R for every element a ∈ A.”

Let R be the relation on the set of ordered pairs of positive integers such that ((a, b), (c, d)) ∈ R if and only if a + d = b + c. Show that R is an equivalence relation Read More »

Suppose that A is a nonempty set, and f is a function that has A as its domain. Let R be the relation on A consisting of all ordered pairs (x, y) such that f (x) = f (y)

Let’s refresh the relevant definitions for this exercise. Definition: “A relation on a set A is called an equivalence relation if it is reflexive, symmetric, and transitive.” Definition: “A relation R on a set A is called reflexive if (a,a) ∈ R for every element a ∈ A.” Definition: “A relation R on a set

Suppose that A is a nonempty set, and f is a function that has A as its domain. Let R be the relation on A consisting of all ordered pairs (x, y) such that f (x) = f (y) Read More »

Show that the relation of logical equivalence on the set of all compound propositions is an equivalence relation. What are the equivalence classes of F and of T? 

As usual, let’s start with the definitions. Definition: “The compound propositions p and q are called logically equivalent if p ↔ q is a tautology. The notation p ≡ q denotes that p and q are logically equivalent.” Notice that if p ↔q is a tautology, p and q have the same truth values. Definition:

Show that the relation of logical equivalence on the set of all compound propositions is an equivalence relation. What are the equivalence classes of F and of T?  Read More »

Which of these relations on {0, 1, 2, 3} are equivalence relations? Determine the properties of an equivalence relation that the others lack.

I found out that some students want to solve this type of exercise, where they need to answer if a relation is an equivalence relation, but they don’t know what an equivalence relation is. By doing this, you have a high probability of answering wrong. So, let’s start with the definitions. Definition: “A relation on

Which of these relations on {0, 1, 2, 3} are equivalence relations? Determine the properties of an equivalence relation that the others lack. Read More »

How many nonzero entries does the matrix representing the relation R on A={1,2,3,…,100} consisting of the first 100 positive integers have if R is

a) {(a,b)|a>b}? To answer this exercise, let’s find out how many 1s will have in each row. Then, we add them up. The last row (row 100) will have ninety-nine 1s because 99 numbers are less than 100 in the set A={1,2,3,…,100}. The second last row (row 99) will have ninety-eight 1s as 98 numbers

How many nonzero entries does the matrix representing the relation R on A={1,2,3,…,100} consisting of the first 100 positive integers have if R is Read More »

How can the matrix representing a relation R on a set A be used to determine whether the relation is irreflexive?

This is an interesting type of exercise. To make easier this exercise, let’s write an irreflexive relation, represent it using a matrix, and find out what are the characteristics of such a matrix. But first, let’s refresh what an irreflexive relation is. Definition: “A relation R on the set A is irreflexive if for every

How can the matrix representing a relation R on a set A be used to determine whether the relation is irreflexive? Read More »

List the ordered pairs in the relations on {1, 2, 3} corresponding to these matrices (where the rows and columns correspond to the integers listed in increasing order). 

In this case, we are given the matrix that represents the relation, and we need to write the pairs that belong to the relation. It is the opposite of this exercise. a) Matrix 1 The approach to solving this type of exercise is to find where there is a 1 in the matrix and write

List the ordered pairs in the relations on {1, 2, 3} corresponding to these matrices (where the rows and columns correspond to the integers listed in increasing order).  Read More »