Closure of an open ball is equal to the closed ball (Euclidean space)
50344
What is the closure of an open ball $B_X(\mathbf{a},r)$ in $X=\mathbb{R}^n$?
27661
The closed graph theorem in topology
59424
Showing that $B=\{(x,y) \in \Bbb{R^2} \mid \ xy>0 \}$ is an open set
47680
Prove that the union of the interior of a set and the boundary of the set is the closure of the set
72468
Open and closed balls in $C[a,b]$
28683
Sum of two closed sets in $\mathbb R$ is closed?
94825
Open set as a finite union of closed sets
158569
Proving a particular subset of $R^n$ is closed
11405
If a nonempty set of real numbers is open and closed, is it $\mathbb{R}$? Why/Why not?
12467
Why does this proof work: Closed unit ball in $C_0$ is not compact
20810
Boundary of Ball of radius R has zero measure
128894
About compactness and completeness of set $X = \mathbb{R}$ with the metric $d(x, y) = \frac{|x-y|}{1+|x-y|}$
15480
Open set in a metric space is union of closed sets
23721
Prove that the Gaussian Integer's ring is a Euclidean domain
150468
Example of two open balls such that the one with the smaller radius contains the one with the larger radius.
107321
How to show convexity of a ball in metric space?
21176
Closure of the set in dictionary order topology.