Is this set "not closed"?
129227
An example of neither open nor closed set
56581
Possibility to object to closing?
106944
Is the set defined by y=sin(1/x) open or closed?
130975
Given a pair of continuous functions from a topological space to an ordered set, how to prove that this set is closed?
13906
How to prove the set $S$ is closed under the binary operation $a*b=a+b+kab$?
123097
What does the little number following "closed" signify in flag history?
56171
Is $K(X)$ never algebraically closed?
82825
Proving set of interiors is open
126897
Showing the set $A+B$ is closed.
127972
Can distance between two closed sets be zero?
45508
Is the empty set a group?
16281
"Closed by" is incorrect
125962
The set $A'$ is closed in a $T_1$ space
73130
A simple question about open set
144383
The closure of a connected set in a topological space is connected
78117
Closed property of nonempty finite set
10180
How to prove that this set is closed?