General topology

For any discussions about general topology. For instructions h...
Sep 5, 2022 01:36
Henno Bransdma :) ..I miss him too. His answers so beautiful, and clear, and he showed kindness when someone asked for doubts. He helped me a lot, when i was taking my undergrad first general-topology course, and that's why I included him in the acknowledge of my thesis;
2
May 5, 2022 17:04
@MartinSleziak :)
May 5, 2022 03:32
1
A: Prove that if $Z\subseteq Y$, then $(g\circ f)^{-1}(Z)=f^{-1}(g^{-1}(Z)).$

Martin SleziakThe part (a) is not answered here - so let me include it, for the sake of completeness.$\newcommand{\inv}[1]{{#1}^{-1}}$ We want to show that $\inv{(g\circ f)}(Z)=\inv f(\inv g(Z))$. For any $w\in W$ we have: $w\in \inv{(g\circ f)}(Z)$ $\Leftrightarrow$ $(g\circ f)(w)\in Z$ $\Leftrightarrow$ $g(...

Apr 22, 2022 15:07
@MartinSleziak Interesting
 

 Mathematics

Associated with Math.SE; for both general discussion & math qu...
May 22, 2022 00:57
if this persist, you could report to moderators, either on the chatroom or flags. I've seen a few times that this is reported there
 

 Martin Sleziak's room

Miscellaneous (not suitable elsewhere)
May 15, 2022 22:59
Elsewhere, in the world, I think professors day is october 5th
May 15, 2022 22:58
btw Martin, happy day!! AFAIK, you're a professor; well, today, in Mexico, it's professors day.
May 15, 2022 22:52
Martin finding -woah- pics
May 15, 2022 22:52
@MartinSleziak Have you seen a bigger than this one? :p
Apr 3, 2022 17:43
@MartinSleziak yes, Martin
Apr 2, 2022 03:46
ayyyy ay Martin
Apr 2, 2022 03:45
" Of course, I do make mistakes and even with best intentions... "
Mar 25, 2022 18:24
ok bye
Mar 25, 2022 18:23
no really
Mar 25, 2022 18:23
reallly I need to go
Mar 25, 2022 18:22
Martin, I have to go...........................................................
Mar 25, 2022 18:17
:) well gotta go now.
Mar 25, 2022 18:16
gooooood. You know that's the good part, sometimes you might get an: ouch!, but then day by day, it heals, ok? even if it's just slowly! it will be over. And for those that easy forget about it, they should get a temporal tattoo stating "shhhh! shut up. It will be over"
Mar 25, 2022 18:13
"I had"
Mar 25, 2022 18:12
oh ok, so it's over :)
Mar 25, 2022 18:04
good good
Mar 25, 2022 17:59
did you feel symptoms? It's been 7 days since then.
Mar 25, 2022 17:58
Oh well Martin,
Mar 25, 2022 17:57
@MartinSleziak :O!!!
 

 CURED

For feedback/discussion/requests of Close/Undelete/Reopen/Edit...
Apr 22, 2022 21:35
I don't understand why the was removed from here math.stackexchange.com/questions/4433525/…
Apr 22, 2022 19:44
First time that I see something like that..
Apr 22, 2022 19:44
:) see the funny " * still editing * "
Apr 22, 2022 19:43
0
Q: Let $\mathcal{U}$, $\mathcal{U}'$ be bases for $V$ and $W$, respectively. Suppose $f : V \rightarrow W$ is continuous.

kishLet $~\mathcal{U}, \mathcal{U}'$ be bases for $V$ and $W$, respectively. Suppose $f : V \rightarrow W$ is continuous. Let $v_0 \in V$ and $ U \in \mathcal{U}'$ such that $f(v_0) \in U$. Show that there exists $T \in \mathcal{U}$ such that $f(T) \subseteq U $. My approach: * still editing * By def...

Apr 21, 2022 21:47
@XanderHenderson Indeed, you're right. Thanks.
Apr 21, 2022 21:42
@XanderHenderson hmm but then this "To be used for questions whose central topic is a request for examples where a mathematical property holds, or counterexamples where it does not hold. This tag should be used in conjunction with another tag to clearly specify the subject." ? from the tag [examples-counterexamples] description
Apr 21, 2022 20:32
Do you have an idea of why was that?
Apr 21, 2022 20:31
@XanderHenderson I'm confused about an edit I suggested here math.stackexchange.com/questions/3303713/… , I included the tag but it was rejected.
Apr 20, 2022 18:08
@XanderHenderson oh ok, thanks
Apr 20, 2022 17:05
@XanderHenderson ok, thanks. I found 4 dupe questions: me thinks the main question should be math.stackexchange.com/questions/2594322 and the other 3 the duplicates: math.stackexchange.com/questions/3359015 math.stackexchange.com/questions/1976517 math.stackexchange.com/questions/1431179
Apr 20, 2022 16:03
@XanderHenderson When choosing a duplicate, the chosen should be oldest? or could be the, say, more recent question, which at the same time has more answers and reputation?
 

 Tagging

When should a tag be added
Apr 5, 2022 22:44
Apr 5, 2022 22:43
After all, my edit was accepted but, I noticed :) that first it was "rejected" and then this thing: >"This edit introduces tags that do not help to define the topic of the question. Tags should help to describe what the question is about, not just what it contains."
Apr 5, 2022 22:28
About the use of the examples-counterexamples tag: so there's a post, in which (at some point) OP mentions the possibility of finding an example. Should the tag be added?
Apr 3, 2022 22:30
I think the backpropagation tag should be merged to the AI. And when someone ask, could be AI+multivariable calculus
Apr 3, 2022 15:58
So it fits the proof word
Apr 3, 2022 15:57
If one has an integral, then in general, one is supposed to find the result. One doesn't know what that value is. So is a solution to find. On the other side, when it comes to a proof, then one has the statement and one already know what is to be found.
Apr 3, 2022 15:53
For example,
Apr 3, 2022 15:52
@MartinSleziak I think yes.
 

 Math Meta Chat

Chat-room for Math Meta stuff (for moderator-related stuff go to
Mar 27, 2022 20:23
Xander I think you meant downvote instead of vote, second line of the above link
Mar 25, 2022 17:52
well Martin, I replied to the comment about the policy culture
Mar 25, 2022 17:48
@MartinSleziak
Mar 24, 2022 14:36
@XanderHenderson Perhaps this could be expressed on meta. For example, I didn't know that first scenario..
 
Mar 23, 2022 01:08
More over, I don't remember ever using the \begin group \end group here on MSE
Mar 23, 2022 01:08
@Buraian I also don't know. Ask Martin :)
Mar 22, 2022 22:30
just to avoid misunderstandings, I didn't know the word in english for the fruit I was referring to, but I got it now "cranberry"