is ∀x∃y(Lxy) and ∃x∀yLyx provable from each other?
136427
Given $∃y.∀x.p(x,y)$, use the Fitch system to prove $∀x.∃y.p(x,y)$
105233
Is there a counterexample for the claim: if $A \oplus B\cong A\oplus C$ then $B\cong C$?
79407
How to solve ~(P → Q) : P & ~Q by natural deduction?
14161
Proof of when is $A=X^TX$ invertible?
37415
Determine source of ⌘⌥\ being an alias of ⌘C
98320
True or false? $\bigwedge_{i \in I} \bigvee_{j \in J}a_{i,j} \equiv \bigvee_{j \in J} \bigwedge_{i \in I}a_{i,j}$
88281
Mixing and Distributing Qualifiers ($\forall x$, $\exists x$)
28088
When is $f_{xy}(x,y)\neq f_{yx}(x,y)?$
95601
Is the multiplication operator on $\ell^p$ compact?
130998
Is $\exists x \in A ~:~ P(x)$ the same as $\exists x ~:~ x \in A \implies P(x)$
119888
Is it possible to convert $\forall$ quantifiers to $\exists$ quantifiers without negation?
82739
Why is $\alpha \rightarrow \forall x(\alpha)$ not generally correct in first-order logic?
140190
Binary operation $xy$, has identity, but not associativity. Is the inverse unique?
90566
There exists surjections from A onto B and vice versa, and there is no bijection between the sets?
33702
Is this an isomorphism possible?
20571
In a monoid, does $x \cdot y=e$ imply $y \cdot x=e$?
103045
Composition of Proximal Operators