Without truth tables, how can I deduce that P → Q ≡ ¬P ∨ Q?
93557
Intuitively, why does (B → S) ≡ (¬B ∨ S)?
111797
Without computers, how can you conjecture the (in)validity of a long convoluted argument in Predicate Logic?
46939
Natural deduction, Proof $\vdash$ $P\Rightarrow(Q\Rightarrow P)$
101741
Selection of logical connectives {¬,∨,∧,⇒,⇔} in set theory?
148239
natural deduction proof with De Morgan's laws
116978
Trying to prove $p,p \to (r \to q) \vdash (\neg q \to \neg r)$ by using natural deduction.
77759
How do i prove that $(p \vee q) \wedge (\neg p \vee r) \rightarrow (q \vee r)$ is a tautology without using the truth table?
32009
Prove $\;\big((p\rightarrow q) \lor (p \rightarrow r)\big) \rightarrow (q\lor r)\equiv p \lor q \lor r$ without use of a truth table.
51369
Natural deduction proof of $p \lor (p\implies q)$ with propositional calculus
100421
How to write this boolean expression using only NOR gates?
72144
Show that $\mathbb Q(\sqrt p) \not\simeq\mathbb Q(\sqrt q)$
93410
How to prove ~ (~P & ~Q) : P ∨ Q by natural deduction
150053
Is "$(P \land Q) \to P$" a tautology?
25496
Avoiding proof by induction
10598
Contrapositive Fitch Proof
121720
Given ∃x.¬p(x), use the Fitch System to prove ¬∀x.p(x).
50178
\qed for theorems without proofs