Proving $((A \to B) \to B) \to B$ is a tautology
31299
Using the Fitch system, how do I prove $((p \implies q) \implies p)\implies p$?
75199
$a \equiv b \pmod n$ and $c\equiv d \pmod n$ implies $ac \equiv bd \pmod n$
100399
A doubt with a part of a certain proof.
139064
Show by using logical connectives laws that $(P\to Q) \land (Q \to R) $ is equivalent to $(P \to R) \land [(P \iff Q) \lor (R \iff Q)]$
108367
proving tautologically equivalent
139841
Proving $A\setminus(B\setminus C)$ is not equal to $(A\setminus B)\setminus C$
115606
Proofs involving $ (A\setminus B) \cup (A \cap B)$
16092
How to prove that the composition of two surjective functions is surjective
46147
Proving $(\forall a\in\mathbb{Z^+})(m\in\mathbb{Z^+}\to a^m\equiv a^{m-\phi(m)}\pmod{m})$
93742
Show that the conditional statement is a tautology without using a truth table
150053
Is "$(P \land Q) \to P$" a tautology?
146795
Proof If $AB-I$ Invertible then $BA-I$ invertible.
64656
how do you prove that $A\times (B\setminus C) = (A\times B) \setminus (A\times C)$?
152817
Proving $\sup B=\inf A$
83475
Prove Or Disprove: tr(AB)=tr(A)*tr(B)
65379
Deriving $\neg R$ from $\{R↔(R∨(P∧¬P)), R↔¬P, ¬P→(P↔(Q→Q)), P→Q\}$
135986
Show if $a \equiv b \pmod{m}$ then $ac \equiv bc\pmod{mc}$