# Questions tagged [propositional-logic]

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### What is the set of all minimal 3CNF formulas?

Definition: A minimal 3CNF formula is an unsatisfiable 3CNF formula with minimum clauses connected by conjunctions, where each clause is disjunction of 3 literals, that is if any of it's clauses is ...
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### Operator precedence in propositional logic

there is some kind of priorities for the elements in propositional logic ? for example : p ∧¬q → r , given this ,we there may be two options (p ∧¬q) → r OR p ∧ (¬q → r) , which one is the correct ?...
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### Getting a variable assignment of a Tseitin transformed formula

Let $\phi$ be a Boolean formula and $\mathrm{Tseitin}(\phi)$ the corresponding Tseitin transformed equisatifiable formula. It is well-known that one can get a variable assignment for $\phi$ by ...
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### Can proof by contradiction work without the law of excluded middle?

I was recently thinking about the validity of proof by contradiction. I’ve read for the past few days things on intuitionistic logic and Godel’s theorems to see if they would provide me answers to my ...
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### What does the structure ($S_t^x P$) in this Existantial Instantiation imply, Skolemization?
Assume I have two Horn formulas $\phi_1, \phi_2$. Horn formulas are CNF formulas so that each clause has at most one unnegated literal. For example: \$x_1 \wedge (\neg x_1 \vee \neg x_2 \vee x_3 )\...