Natural Deduction: $p \to (\neg q \leftrightarrow (r \lor s)), \neg s \vdash (p \land \neg q) \to r$
92492
Natural Deduction: $(p \lor q)\to r\vdash p \to r$ and $p\to\neg q\leftrightarrow(r\lor s),\neg s\vdash (p\land \neg q)\to r$
52585
How to prove that $[(p \to q) \land (q \to r)] \to (p \to r)$ is a tautology without using the truth table?
20581
How to show that $\Gamma\vdash (\varphi\to\neg\varphi)\to\varphi$?
87955
How to prove that $P \rightarrow Q$ is equivalent with $\neg P \lor Q $?
139537
Show that $x\subseteq y \Leftrightarrow \mathcal{P}(x)\subseteq\mathcal{P}(y)$.
76347
Shorter proof for some equvalences
147947
Does double negation distribute over implication intuitionistically?
142526
What's the intuition behind difference of $\neg(S\land E)$ and $\neg S \land \neg E$?
35427
Natural Deduction - How to define literals?
157924
$\forall x\in\mathbb{N}[(\exists y\in\mathbb{N}(2\leq y\land y<x\land y\ |\ x))\to(\exists z\in\mathbb{N}(2\leq z\land z\leq\sqrt x\land z\ |\ x))]$
119888
Is it possible to convert $\forall$ quantifiers to $\exists$ quantifiers without negation?
104871
Direct cut-elimination for natural deduction.
132532
Things around $(\forall x)(\Psi \Rightarrow \Phi) \Leftrightarrow ((\exists z)\Psi) \Rightarrow \Phi)$
83037
Applying Zorn's Lemma to natural numbers
48368
Prove using Natural Deduction in predicate logic $(\forall x\ P(x))\to Q ⊢ \exists x (P(x)\to Q)$
83023
From axiom of regularity, how can I prove $x \notin y \lor y \notin x$
87257
How to prove this sequent using natural deduction?