How to prove that $\{\land,\lnot\}$ is complete?
89127
How do I prove if a set of operations is complete?
123458
Prove $( \lnot C \implies \lnot B) \implies (B \implies C)$ without the Deduction Theorem
104068
Prove that $\forall a,b\in\mathbb{C} \exists c,d \in \mathbb{C}: c+d = a \land cd = b$
4518
How would one go about proving that the rationals are not the countable intersection of open sets?
118898
Is there a simple way of proving that $\text{GL}_n(R) \not\cong \text{GL}_m(R)$?
32910
Completion and algebraic closure commutable
78804
Proving that $\mathscr L=\{0^n \big|\text{n is the square of a natural number }\}$ is non regular using the pumping lemma
151295
Proving $|S \times \mathbb{N}|=|S|$ when $S$ is an infinite set
89468
Space Sobolev $W^{m,p}$ complete
3296
Proof That $\mathbb{R} \setminus \mathbb{Q}$ Is Not an $F_{\sigma}$ Set
115606
Proofs involving $ (A\setminus B) \cup (A \cap B)$
84251
Show that $\Gamma \cup \{\neg \phi\}$ is satisfiable if and only if $\Gamma\not \models \phi$
149820
How do you prove the set $G = \{(x, f(x)) \mid x \in \mathbb R\}$ is closed?
21820
How to prove that a set is invariant?
75625
Complete residue system proof
52585
How to prove that $[(p \to q) \land (q \to r)] \to (p \to r)$ is a tautology without using the truth table?
52629
Example 1, Sec. 22 in Munkres' TOPOLOGY, 2nd edition: How to verify that this map is closed?