Example of subset of $\mathbb{R}²$ such that $A\neq A'\neq A''\neq A'''$?
35723
Accumulation points of accumulation points of accumulation points
109305
Non-existence of natural numbers such that $\sqrt{n} +\sqrt{n+1} <\sqrt{x} +\sqrt{y} <\sqrt{4n+2}$
19754
$\mathbb{R}$ \ $\mathbb{Q}$ and $\mathbb{R}^2\setminus\mathbb{Q}^2$ disconnected?
36631
Is $[0,1] \cap \Bbb Q$ a compact subset of $\Bbb Q$?
48162
Is the subset $[0, \sqrt2] ∩\mathbb{Q} ⊂ \mathbb{Q}$ closed, bounded, compact?
93771
Prove that for any set $A$ there is some $x \notin A$
42774
Examples of involutions on $\mathbb{R}$
63701
An example of a regular function over an open set
89257
Give an example of a function $f:\mathbb{R}^2 \mapsto \mathbb{R}^2$ such that
81927
Example of closed and bounded in $\mathbb Q$ set that is not compact
73154
Compact subset in colimit of spaces
139988
Counter example for a result of intersection of subspaces
144246
Subset of $\mathbb{R}^n$ homeomorphic to $\mathbb{R}^n$
45405
An elementary way to show any bounded subset of $\Bbb{R}^k$ is totally bounded
25764
Example of a ring such that $R^2\simeq R^3$, but $R\not\simeq R^2$ (as $R$-modules)
67259
Can we prove that a bounded closed subset of $\mathbb R^n$ is compact without Axiom of Choice?
62208
If $A$ is a non-empty set, then $A \notin A$