How Can Equivalence Relations Determine Equal Classes?

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Discussion Overview

The discussion revolves around proving a property of equivalence relations, specifically that if ~ is an equivalence relation on a set s and [a] denotes the equivalence class of a in s under ~, then a ~ b if and only if [a] = [b]. Participants are seeking guidance on how to approach this proof, which is related to mathematical reasoning and conceptual understanding of equivalence relations.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Conceptual clarification

Main Points Raised

  • One participant expresses confusion about how to start the proof and asks for hints on approaching the problem.
  • Another participant suggests that the proof follows directly from the definition of equivalence relations and prompts consideration of the implications if [a] ≠ [b].
  • A different participant proposes that if [a] ≠ [b], then there must be an element in one equivalence class that is not in the other, leading to a contradiction of the assumption that [a] = [b].
  • One participant challenges the assumption that an equivalence relation is simply a relation satisfying a, b in s, indicating that this understanding is insufficient.
  • There is a suggestion that the participants should refer back to their textbooks or class notes for a clearer understanding of equivalence relations.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the proof approach, and there are differing levels of understanding regarding the definition of equivalence relations. Some participants express confusion, while others attempt to clarify the concepts involved.

Contextual Notes

There is an indication that some participants may lack a complete understanding of equivalence relations, which could affect their ability to engage with the proof effectively. The discussion also highlights the need for clarity on definitions and properties related to equivalence classes.

Tokenfreak
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I am trying to prove this as I am practicing for a test but I am pretty much clueless on this problem:

Prove that if ~ is an equivalence relation on a set s and [a] denotes the equivalence class of a in s under ~, then a ~ b if and only if [a] = .


If anyone can give me some points on how to approach or start this problem it would be great. Thanks.
 
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Tokenfreak said:
I am trying to prove this as I am practicing for a test but I am pretty much clueless on this problem:

Prove that if ~ is an equivalence relation on a set s and [a] denotes the equivalence class of a in s under ~, then a ~ b if and only if [a] = .


If anyone can give me some points on how to approach or start this problem it would be great. Thanks.


It falls directly out of the definition of equivalence relation, so it's tricky to think of a hint. But what happens if [a] \neq ? Then there must either be an element in ____ that's not in ______ or vice versa. Then what?
 
So would it be safe to assume that an equivalence relation ~ on a set s is a relation satisfying a,b in s. If [a] != , then there must be an element in a that's not in b or vice versa. Therefore, this contradicts that [a] = .Is this close? I am pretty much clueless on this proof.
 
Tokenfreak said:
So would it be safe to assume that an equivalence relation ~ on a set s is a relation satisfying a,b in s.

No. You need to go back to your book and read what an equivalence relation is.

Aren't a and b assumed to be elements of s? So a,b in s is true of all a and b in s. Has nothing to do with equivalence relations.


Tokenfreak said:
If [a] != , then there must be an element in a that's not in b or vice versa. Therefore, this contradicts that [a] = .


Well yes, if you assume [a] != then that contradicts [a] = . Isn't that always the case no matter what [a] and are?

I think you need to read your text and/or class notes to understand what an equivalence relation is.
 
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