In a formal language, how does one show that $\neg \neg \bot \neq( \phi \wedge \psi) $
10644
Why $¬¬\bot \not\in PROP$?
15300
How to show that $(W^\bot)^\bot=W$ (in a finite dimensional vector space)
2162
How does one actually show from associativity that one can drop parentheses?
150385
The use of the Axiom of Choice in this proof of the sequence lemma
50804
It seems obvious, but how to prove it formally?
48213
proving logical equivalence $(P \leftrightarrow Q) \equiv (P \wedge Q) \vee (\neg P \wedge \neg Q)$
10598
Contrapositive Fitch Proof
58663
How to show that if $\phi(n)$ equals to n itself, then n must be 1?
84251
Show that $\Gamma \cup \{\neg \phi\}$ is satisfiable if and only if $\Gamma\not \models \phi$
113605
In Fitch, how does one prove "(P → Q)" from the premise "(¬P ∨ Q)"?
87257
How to prove this sequent using natural deduction?
72185
The negation of a limit condition, Spivak style.
124424
How to show that there is a deduction of $\varphi\leftrightarrow\psi$
35115
Questions on how to prove that a set of connectives is NOT functionally complete
138897
help with some Hilbert style proofs in a propositional logic axiom system.
88104
Prove "$(p \lor q) \land (\neg p \lor r)) \rightarrow (q \lor r)$" is a tautology
145759
formal proof from calulus