Question

Natural deduction proof: {A → B, B → (C & D), ¬C v ¬D} ⊢ ¬A

score 4.5k · Answer 1 · 2026-03-27 11:46:18

4.5k

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Natural deduction proof: {A → B, B → (C & D), ¬C v ¬D} ⊢ ¬A

Published on 27 Mar 2026 - 11:46

score 1.2k · Answer 2 · 2026-03-27 11:46:24

1.2k

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Prove that the following argument is valid

Published on 27 Mar 2026 - 11:46

score 235 · Answer 3 · 2026-03-27 14:52:51

235

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A Natural-Deduction proof of $ \{ \neg N,\neg N \to L,D \leftrightarrow \neg N \} \vdash (L \lor A) \land D $.

Published on 27 Mar 2026 - 14:52

score 152 · Answer 4 · 2026-03-27 14:52:52

152

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Prove that the set of sentences $\{A \land (B \lor C), (\lnot C \lor H) \land (H \rightarrow \lnot H), \lnot B\}$ is inconsistent

Published on 27 Mar 2026 - 14:52

score 109 · Answer 5 · 2026-03-25 14:28:47

109

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Context-free language or not

Published on 25 Mar 2026 - 14:28

score 2.1k · Answer 6 · 2026-03-27 14:59:09

2.1k

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Prove by Natural deduction that $\lnot\exists xP(x)\rightarrow\forall x\lnot P(x)$

Published on 27 Mar 2026 - 14:59

score 119 · Answer 7 · 2026-02-23 06:39:41

119

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Prove using Hilbert calculus $\forall x(Px\rightarrow x\equiv a)\vdash Pb\rightarrow Pa$, formal proof.

Published on 23 Feb 2026 - 6:39

score 133 · Answer 8 · 2015-05-30 23:20:00

133

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Strange sum of random variables

Published on 30 May 2015 - 23:20

score 1.9k · Answer 9 · 2015-06-08 21:52:52

1.9k

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Prove that there are no positive integers $a$ and $b$, such that $b^4 + b + 1 = a^4$

Published on 08 Jun 2015 - 21:52

score 95 · Answer 10 · 2015-06-27 16:14:44

95

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Is this mathematical statement?

Published on 27 Jun 2015 - 16:14

score 6.5k · Answer 11 · 2015-07-06 10:53:13

6.5k

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How to prove a logical implication?

Published on 06 Jul 2015 - 10:53

score 1.1k · Answer 12 · 2015-07-06 13:02:47

1.1k

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How to show that $[(p \rightarrow q) \rightarrow r] \Rightarrow [p \rightarrow (q \rightarrow r)]$

Published on 06 Jul 2015 - 13:02

score 646 · Answer 13 · 2015-07-13 06:37:48

646

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$A⇒(B \lor C)$ and $[(A \Rightarrow B) \lor (A \Rightarrow C)]$

Published on 13 Jul 2015 - 6:37

score 371 · Answer 14 · 2015-07-13 10:39:04

371

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Formal proof of $(A\lor B)∨C \leftrightarrow A\lor(B\lor C)$

Published on 13 Jul 2015 - 10:39

score 247 · Answer 15 · 2015-07-13 14:31:45

247

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Proof of deduction theorem without induction

Published on 13 Jul 2015 - 14:31

List Question

Natural deduction proof: {A → B, B → (C & D), ¬C v ¬D} ⊢ ¬A

Prove that the following argument is valid

A Natural-Deduction proof of $ \{ \neg N,\neg N \to L,D \leftrightarrow \neg N \} \vdash (L \lor A) \land D $.

Prove that the set of sentences $\{A \land (B \lor C), (\lnot C \lor H) \land (H \rightarrow \lnot H), \lnot B\}$ is inconsistent

Context-free language or not

Prove by Natural deduction that $\lnot\exists xP(x)\rightarrow\forall x\lnot P(x)$

Prove using Hilbert calculus $\forall x(Px\rightarrow x\equiv a)\vdash Pb\rightarrow Pa$, formal proof.

Strange sum of random variables

Prove that there are no positive integers $a$ and $b$, such that $b^4 + b + 1 = a^4$

Is this mathematical statement?

How to prove a logical implication?

How to show that $[(p \rightarrow q) \rightarrow r] \Rightarrow [p \rightarrow (q \rightarrow r)]$

$A⇒(B \lor C)$ and $[(A \Rightarrow B) \lor (A \Rightarrow C)]$

Formal proof of $(A\lor B)∨C \leftrightarrow A\lor(B\lor C)$

Proof of deduction theorem without induction

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