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comment Assistance in proving a tautology using a series of logical equivalences.
Which logical equivalences can you use? Can you use any deductive rules of inference which aren't equivalences?
Aug
29
awarded  Necromancer
Aug
23
answered Proof using deductive system and modus ponens
Aug
23
answered Is the replacement theorem true for conditionals?
Aug
13
comment Is the following a correct logical proof?
" Then at the last step P should be derived outside of ¬P after deriving ¬¬P." That all depends on the system involved. In some systems, if you can derive a contradiction, then you can discharge a negation into the complementary literal. CCNpKqNqp, and CCNpqCCNpNqp both come as tautologies which back up using such a rule of inference.
Aug
11
revised Is the following a correct logical proof?
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Aug
11
comment Is the following a correct logical proof?
This doesn't answer the question.
Aug
11
answered Is the following a correct logical proof?
Aug
6
comment Are the logical [equivalence] laws sound and adequate without de Morgan's law?
The laws referred to the author might come as equational and there might not exist any natural deduction rules of inference than can get used.
Aug
6
comment Are the logical [equivalence] laws sound and adequate without de Morgan's law?
This is rather unclear. It would come as clearer if the logical laws got expressed in symbolic form. From what you've said, the commutative property of logical equivalence and the associative property of logical equivalence, could come as axioms. I have a feeling though that you meant the comutative property of logical disjunction, and the commutative property of logical conjunction. You might also want to state how "sound" and "adequate" get defined also.
Aug
6
comment Show that $A \lor B ⊢ B \lor A$
I can guess that you have a disjunction elimination rule. But, I'm not so sure as to whether you have one or two disjunction elimination rules. For a proof try to assume each disjunct and see if you can derive the conclusion using disjunction introduction. Then discharge both of those sub-proofs (or conditionals, if your system works with conditionals instead of sub-proofs) and the disjunction using disjunction elimination.
Jul
27
comment What is $0\div0\cdot0$?
You didn't tell us what the set of numbers was. If you keep the set of numbers in mind, it becomes clearer that there is no such thing, since division on the natural numbers is VERY unlike division on the real numbers, especially in comparison to multiplication on the natural numbers and real numbers respectively.
Jul
27
revised What is $0\div0\cdot0$?
added 431 characters in body
Jul
27
answered What is $0\div0\cdot0$?
Jul
27
comment Max/Min to logical operator transformation and viceversa
What set of numbers are those inequalities supposed to apply to?
Jul
26
revised Law of Clavius explained
added 83 characters in body
Jul
26
revised Law of Clavius explained
added 17 characters in body
Jul
26
comment Law of Clavius explained
@skyfire I've added a link to an entry on Polish notation.
Jul
26
revised Law of Clavius explained
added 72 characters in body
Jul
26
revised Law of Clavius explained
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