Show that $\lnot\exists x\in A P(x) \equiv\forall x\in A\lnot P(x)$
67490
Restricing domains for universal and existential quantifiers
123458
Prove $( \lnot C \implies \lnot B) \implies (B \implies C)$ without the Deduction Theorem
49621
Proof of "well-founded iff there is no sequence $x_n$ s.t. $(x_{n+1}, x_n) \in R$"
76347
Shorter proof for some equvalences
49994
Deduction of $\forall y \exists x (x=y)$
135700
Show that $\lim_{n \to \infty} (1/n)\sum_{i=1}^n f(x_i)$ exists
14215
Show that the union $\bigcup A_n$ has empty interior in $X$
76148
Show that $\exists c \in \mathbb{R} : f(c) = 0$
137511
Trying to show that $\sup \{b^p:p\in Q,\;0<p<x\} = \inf\{b^q:q\in Q,\;x<q\}$
29655
$L^p$ and $L^q$ space inclusion
63124
Show that $ \lVert A \rVert_2^2 \leq \lVert A \rVert _1 \lVert A \rVert _ \infty $
20467
Show that $(y_n)\in l^q$
155974
Show $||Tx||_2 \leq ||(v_n)||_2 \cdot ||x||_{\infty}$
102478
$X_n\leq Y_n$ implies $\liminf X_n \leq \liminf Y_n$ and $\limsup X_n \leq \limsup Y_n$
115004
If $x\notin\mathbb Q$, then $\left|x-\frac{p}{q}\right|<\frac{1}{q^2}$ for infinitely many $\frac{p}{q}$?
140194
Using natural deduction to prove that $p \implies q \vdash \lnot p \lor q$
149416
Show that $ \{\lnot,\leftrightarrow\} $ is not functional complete