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xoux
  • Member for 2 years, 2 months
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3 votes
3 answers
320 views

Why is any sentence a logical consequence of a set of inconsistent premises?

2 votes
1 answer
79 views

How to understand scope of action of a quantifier in a quantified sentence that is a translation of an English sentence?

1 vote
2 answers
182 views

How to understand a proof by contradiction in minute detail?

1 vote
1 answer
134 views

How to formally prove using first-order set theory that {7,8,9}={7,8,10} is a false statement?

1 vote
1 answer
70 views

Prove that if S tautological consequence of P, S tautological consequence of Q, then S tautological consequence of P | Q

1 vote
1 answer
162 views

How to write a formal proof of Euclid's Theorem, specifying every logic rule used?

1 vote
1 answer
90 views

Given a premise and ten axioms about a world with three shapes T, C, and D, how to prove that either all objects are T, all are C or all are D?

0 votes
1 answer
48 views

Is ∃x (∀y (A(x,y) → B(x,y)) → ∃z C(z)) equivalent to ∃x ∃y ∃z ((A(x,y) → B(x,y)) → ∃z C(z))?

0 votes
2 answers
168 views

What is the difference between a logical operator and a logical symbol?

0 votes
2 answers
125 views

How to write that two specific sets are the same set in first-order naive set theory?

0 votes
1 answer
176 views

How to interpret "P ⟺ Q is true if and only if the first-order logic sentence P ↔ Q is logically necessary"?

0 votes
1 answer
101 views

What does it mean, intuitively and then also precisely, that a particular English word is not truth functional?

0 votes
0 answers
399 views

Language, Proof, and Logic: Problem 11.26 How to give both possible translations of an ambiguous English sentence into FOL?