Is <-> an Equivalence Relation on Propositions?

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SUMMARY

The discussion centers on proving that the logical biconditional operator, denoted as A <-> B, is an equivalence relation on propositions. The proof utilizes a contradiction approach, demonstrating that if A implies B and B implies A, then the negation of these implications leads to a contradiction. Additionally, participants emphasize the necessity of verifying the three properties of equivalence relations: reflexivity, symmetry, and transitivity, suggesting the use of truth tables for clarity.

PREREQUISITES
  • Understanding of logical operators, specifically biconditional (A <-> B) and implication (A -> B).
  • Familiarity with proof techniques, particularly proof by contradiction.
  • Knowledge of equivalence relations and their properties: reflexivity, symmetry, and transitivity.
  • Ability to construct and interpret truth tables for logical expressions.
NEXT STEPS
  • Study the properties of equivalence relations in depth, focusing on reflexivity, symmetry, and transitivity.
  • Learn how to construct truth tables for various logical operators, including biconditional and implication.
  • Explore proof techniques, particularly proof by contradiction, through various mathematical examples.
  • Investigate the relationship between logical operators and their representations in propositional logic.
USEFUL FOR

Students of logic, mathematicians, and anyone interested in understanding the foundations of logical reasoning and equivalence relations in propositional calculus.

soopo
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Homework Statement



We have an equivalence relation such that
A <-> B.

Prove that the equivalence relation is true.

The Attempt at a Solution



Let
P: A -> B
Q: B -> A

Let's prove the relation by contradiction.
Assume
\neg A -&gt; \neg B

The previous assumption is the same as Q. Thus, we have a contradiction, since
it is impossible that both of the following Q and \neg Q
are true at the same time, where

Q: B -> A and
\neg Q: \neg A -&gt; \neg B which is the same as B -> A.

Thus, the equivalence relation is true between A and B.
 
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soopo said:

Homework Statement



We have an equivalence relation such that
A <-> B.

Prove that the equivalence relation is true.

Is A <-> B given or is that what you're trying to prove?
 
Are you trying to show that <-> is an equivalence relation on propositions?

If that is the case, you have to show the following three things:

A <-> A for all A.
if A <-> B then B <-> A.
if A <-> B AND B <-> C then A <-> C.

How should you show these? I'd probably use truth tables and the definition if <-> in terms of -> and "AND".
 

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