Quick simple set theory question

In summary, the definitions for ≥ being reflexive, symmetric, transitive, and antisymmetric are: - Reflexive: For any x in X, x≥x is true. - Symmetric: For any x,y in X, if x≥y then y≥x is also true.- Transitive: For any x,y,z in X, if x≥y and y≥z, then x≥z is true.- Antisymmetric: For any x,y in X, if x≥y and y≥x, then x=y is true.- X as a lattice: X is a lattice if any two elements in X have a least upper bound and greatest lower
  • #1
ktheo
51
0

Homework Statement



Let X be a set and ≥ be a binary relation on X
Provide a mathematical definition for

≥ is reflexive
≥ is symmetric
≥ is transistive
≥ is antisymmetric
X is a lattice


The attempt at a solution

So I'm not really sure what this is asking... specifically if ≥ is supposed to be some sort of variable he chose or if I'm missing something and the greater than or equal than means something. But in any case is this this asking me to state the general rules for binary relations? I.E. for reflexive that for any x[itex]\in[/itex]X, xRx? I'm a little confused about what my format to show the definition is in regards to X and ≥
 
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  • #2
ktheo said:

Homework Statement



Let X be a set and ≥ be a binary relation on X
Provide a mathematical definition for

≥ is reflexive
≥ is symmetric
≥ is transistive
≥ is antisymmetric
X is a lattice


The attempt at a solution

So I'm not really sure what this is asking... specifically if ≥ is supposed to be some sort of variable he chose or if I'm missing something and the greater than or equal than means something. But in any case is this this asking me to state the general rules for binary relations? I.E. for reflexive that for any x[itex]\in[/itex]X, xRx? I'm a little confused about what my format to show the definition is in regards to X and ≥

Yes. Just state the definitions and substitute ≥ for R. So reflexive means x≥x for all x in X.
 
  • #3
Dick said:
Yes. Just state the definitions and substitute ≥ for R. So reflexive means x≥x for all x in X.

Awesome cool. So to confirm,for symmetric:

For any x,y[itex]\in[/itex]X, x≥y ----> y≥x is sufficient?
 
  • #4
ktheo said:
Awesome cool. So to confirm,for symmetric:

For any x,y[itex]\in[/itex]X, x≥y ----> y≥x is sufficient?

Yes, I think so. That will not likely be true if you read '≥' to mean 'greater than or equal to', but that looks like what the question is asking for. Just provide the mathematical definition.
 
  • #5
Dick said:
Yes, I think so. That will not likely be true if you read '≥' to mean 'greater than or equal to', but that looks like what the question is asking for. Just provide the mathematical definition.

Okay thanks. He words it exactly as I wrote it out. I just found it a little weird that he uses ≥... but you must be right because in the next question he asks ≥ to be defined by "..." (a condition) so I guess it's just his choice of variable..
 

What is set theory?

Set theory is a branch of mathematics that deals with the study of sets, which are collections of objects or elements. It provides a foundation for other areas of mathematics and has applications in various fields such as computer science, linguistics, and philosophy.

What is a set?

A set is a well-defined collection of distinct objects or elements. These objects can be anything, such as numbers, letters, or even other sets. Sets are denoted by curly braces {} and the elements are separated by commas.

What is the cardinality of a set?

The cardinality of a set is the number of elements in the set. It can be finite, infinite, or even equal to 0. For example, the set {1, 3, 5, 7} has a cardinality of 4, while the set of all even numbers has an infinite cardinality.

What is the difference between a set and a subset?

A subset is a set that contains only elements that are also in another set, called the superset. In other words, all the elements of the subset are also elements of the superset. However, a set may or may not be a subset of another set.

What are the basic operations in set theory?

The basic operations in set theory are union, intersection, and complement. Union combines two sets and includes all elements from both sets. Intersection finds the common elements between two sets. Complement finds all the elements that are not in a given set.

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