List questions from formal-proofs

Published on 26 Mar 2026 - 10:52

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Propositional Logic - Formal Proofs using natural deduction

Published on 19 Oct 2015 - 21:03

6.7k

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If $x_n:=\sqrt{n}$, show that $(x_n)$ satisfies $\lim|x_{n+1}-x_n|=0$, but that it is not a Cauchy sequence.

Published on 23 Oct 2015 - 4:18

28

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Multiplication in $\mathbb{N}$ from two simple laws

Published on 23 Oct 2015 - 13:04

59

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Prove $(A\cup C=B\cup C)\implies(A\mathbin{\Delta} B\subseteq C)$

Published on 07 Mar 2026 - 11:00

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Prove without using truth table

Published on 26 Mar 2026 - 4:35

98

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Proof of $\vdash P \rightarrow (Q\lor P)$

Published on 20 Nov 2015 - 12:20

195

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(Another) Proof within Hilbert system

Published on 21 Nov 2015 - 9:43

59

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Determine all theta satisfying an expression

Published on 22 Nov 2015 - 21:39

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Existential and Universal Equivalence Proof

Published on 26 Nov 2015 - 20:07

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Suppose that $a$ and $b$ are natural numbers such that $a^2 = b^3$. Prove that if $4$ divides $b$, then $8$ divides $a$.

Published on 04 Dec 2015 - 14:50

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Natural deduction: negation of quantifiers

Published on 27 Mar 2026 - 21:23

2.4k

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Di-graphs handshaking lemma proof

Published on 05 Dec 2015 - 5:21

767

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Natural deduction predicate logic for equality

Published on 27 Mar 2026 - 21:16

690

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Is this (tricky) natural deduction with De Morgan's laws correct?

Published on 27 Mar 2026 - 21:18

List Question

Prove f(indexed intersection Ai) is a subset of indexed intersection Ai.

Propositional Logic - Formal Proofs using natural deduction

If $x_n:=\sqrt{n}$, show that $(x_n)$ satisfies $\lim|x_{n+1}-x_n|=0$, but that it is not a Cauchy sequence.

Multiplication in $\mathbb{N}$ from two simple laws

Prove $(A\cup C=B\cup C)\implies(A\mathbin{\Delta} B\subseteq C)$

Prove without using truth table

Proof of $\vdash P \rightarrow (Q\lor P)$

(Another) Proof within Hilbert system

Determine all theta satisfying an expression

Existential and Universal Equivalence Proof

Suppose that $a$ and $b$ are natural numbers such that $a^2 = b^3$. Prove that if $4$ divides $b$, then $8$ divides $a$.

Natural deduction: negation of quantifiers

Di-graphs handshaking lemma proof

Natural deduction predicate logic for equality

Is this (tricky) natural deduction with De Morgan's laws correct?

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