# Requests for Reopen & Undeletion Votes (volume 07/2018 - today)

The purpose of this thread is to help focus the attention of the community on posts that may require reopen and undeletion votes. A request should be posted as an answer below (one request per answer).

Some guidelines:

• Please be polite, and respect the many different viewpoints in our diverse community. This goes for the person making the request as well as those commenting on it.

• There is a reopen queue. Please wait until a post has gone through this queue, before posting here. Notice that the first edit after the question was put on-hold pushes the question into reopen review queue, if the edit was done within 5 days of closure. So does a reopen vote. (If the review has already been finished, it is shown on the timeline of the question.) In doubt, wait 24 hours after the last substantive action.

• To inform readers of the current (and past) states of the targeted post, please add once the request resulted in some action the information Reopened or Undeleted at the start. (If it the action is undone, add this too, like Reopened, reclosed.)

• Do not only post a request, like "request reopening of ". Instead make a case for your concern. Yet keep in mind that it can be easier to get your request handled if you try to frame in a away that takes the feedback the post received into account in a positive way rather then seeking confrontation. Also, try to improve the post before posting here.

• In case of "small" requests, like one missing vote, it can make sense to ask in chat instead of posting here. The room CRUDE is a reasonable place for such requests. The same guidelines apply there.

Earlier versions of this thread that served as a model:

Undeleted

I nominate Is the Balazard-Saias-Yor integral non-positive? for un-deletion and re-opening. Being self-deleted by a deleted user, it has a score of +1 and two stars. The topic adds value to the site and the question asker has put effort in the post.

Currently, only one undelete vote is needed to undelete this question. I hope the two users who starred this question can see their favorite question re-opened.

• It should be noted that "stars" do not necessarily indicate that a user finds the question useful or up to the standards of the site. Many users use stars to keep track of questions with which they have interacted, and desire to return to at some point. For example, I sometimes star questions which lack context or otherwise fail to meet the standards of this site. After downvoting, leaving a comment, and/or voting to close, I will star the post so that I can return to it a few days later to see if it has been improved. If it has, I'll retract my downvote and/or close vote. – Xander Henderson Feb 4 at 17:02
• I'm not saying that this is the case here; I just want to point out that "stars" should not be taken as a sign of quality vis-a-vis undeletion votes. – Xander Henderson Feb 4 at 17:03
• @XanderHenderson Thx for comments. Noted. – GNUSupporter 8964民主女神 地下教會 Feb 5 at 1:27

Undeleted, closed, deleted, re-undeleted, reopened

I nominate How to use derivatives to prove that $f(x)=2\cos^2\left(\frac{\pi }{4}-\frac{x}{2}\right)-\sin \left(x\right)=1$? for undeletion since OP has self-deleted his/her question after receiving an answer. This is unacceptable on Math.SE.

• It's better to write self-contained posts. In the current case for the moment there was no big risk, but it's still not ideal. – quid Nov 8 '18 at 19:42
• @quid Thanks for your intervention. I'll correct this now. – GNUSupporter 8964民主女神 地下教會 Nov 8 '18 at 19:44
• I don't understand why this question was closed and deleted by users. It is not unclear what they're asking. (It may not be true, but it is certainly clear!) – user1729 Feb 5 at 11:28
• @user1729 Some users don't like wrong info in the question. They have standards so high that $D(\sin x)$ and the RHS of $f'(x)$ doesn't please them. It's possible that they used their power to get rid of this question. – GNUSupporter 8964民主女神 地下教會 Feb 5 at 11:37
• It's definitely not unclear—the questioner gives the problem, shows what they did, and asks what's wrong with it. I think it could do with an additional answer which makes crystal clear what the error was and how the (interesting!) technique works, and reopening would allow someone to post that. – timtfj Feb 5 at 12:06
• @timtfj It's now reopened. – GNUSupporter 8964民主女神 地下教會 Feb 5 at 16:04
• @GNUSupporter8964民主女神地下教會 At least it's clear that their expectations could never rise to match the size of your assumptions... – Lord_Farin Feb 6 at 17:34

Undeleted, then deleted again, then undeleted again, then reopened, then closed again, then reopened again

Please undelete Compare $\arcsin (1)$ and $\tan (1)$ because OP has made an observation $$\sin(\tan1)\leq1$$ in order to compare the two quantities in the question title. This question has

• 3 $$\star$$;
• 1 Undelete vote remaining to save this question.

Undeleted and merged with duplicate

I would like to see the question "Finding sum to infinity" undeleted. The OP says that they "tried using the Taylor series for $$e^x$$ but couldn’t figure out how to manipulate it to get the above expression", which seems reasonable. Moreover:

1. The question is a duplicate and is closed as such. It is not standard practice to delete duplicates (see here).
2. The question itself is on +5 (+6/-1), and one of the answers is on +12.
• I don't get the argument. What is the value of keeping that question on the site? – quid Feb 15 at 19:00
• I didn't realiize that "it is standard practice to not delete duplicates." Cite? – Gerry Myerson Feb 16 at 4:06
• @GerryMyerson I also had entertained to comment on that. What arguably is true is that "it is not standard practice to delete duplicates", which of course is not quite the same. – quid Feb 16 at 12:14
• @Gerry What I meant was "a question should not be deleted simply because it is a duplicate" (so I've edited the post to quid's sentence). This was discussed here. – user1729 Feb 18 at 11:28

Merged

Please Consider undeleting the following question:

https://math.stackexchange.com/questions/3203711/what-are-the-steps-to-finding-int-01-frac-ln1-x-lnxx-dx

Of course, this one is a strict duplicate of the one for it was closed. However, regarding the fact that the answers to this question at all are quite spread I would like to draw attention to my own answer given here collecting some of the possible ways to evaluate this integral within one post.

• Would it make sense to merge the thread with the duplicate target? – quid May 4 at 10:11
• @quid That might a better way than undeleting the question, indeed. I'm ashamed to ask, but what exactly does it mean to merge a thread with another one? – mrtaurho May 4 at 10:13
• It means that the answers will be moved to the other thread (and deleted on the original one). The Q can be preserved (like a duplicate) or not. – quid May 4 at 10:16
• @quid That sounds pretty good. Shall I do this, at least with my own answer, by myself or do I have to request for this somewhere? – mrtaurho May 4 at 10:18
• That's something only moderators can do. (Of course you could simply repost your answer on the dupe too, but that would not be merge.) I'll just go ahead and do it now. – quid May 4 at 10:23
• @quid Thank you for your time! – mrtaurho May 4 at 10:24

Undeleted

I nominate Factorising the ideal $(14)$ in $\mathbb{Q}(\sqrt{-10})$ into a product of prime ideals. for undeletion since the question asker has self-deleted his/her own question after receiving an answer. This is unfair the answerer who spent time and effort writing the answer, which deserves evaluation from the community.

Reopened

Please consider reopening Does knowing the surface area of all faces uniquely determine a tetrahedron?. This is a very natural and self-motivating question that does not need any additional context, and it's gotten several great answers.

Reopened

Please consider reopening this post, suitably narrowed since originally closed as "too broad":

Book recommendation... Linear Programming for self-study

I don't believe there has been another such request, and under my pestering the OP has provided context for what sort of self-study they've previously undertaken.

Reopened

Please consider reopening Does non-uniqueness of solution to 1st order ODE implies the existence of infinitely many solutions?.

This is an interesting question about a not so famous result in ODE. The answers points to the correct reference. I've edited the question to include more context.

• I agree it's an interesting question, and the updated text now has enough context, so I initiated reopening it. – John Omielan Jun 18 at 16:36
• @JohnOmielan, if you care, please consider also editing the answer there (to rollback to edit 1). Now that the post is reopened, there is no need for that comment. I tried to edit myself, but the suggested edit got rejected – Arctic Char Jun 19 at 19:20
• I agree the comment there regarding it being closed is no longer pertinent, so I did rollback of the edit. – John Omielan Jun 19 at 19:26

Undeleted, reopened (that was fast!)

What is the maximal number of subsets of a finite set, such that no one is the unions of some other ones? is a serious mathematical question which has attracted two useful answers (full disclosure – one of those two answers is mine). Please have a look and consider casting the third vote to undelete.

Undeleted (and edited the duplicate target)

Three coins are tossed. If one of them shows a tails, what is the probability that all three coins show tails?

This question was marked as a duplicate to another question (created 2014) that was closed and deleted (2018).

• It seems it took 9 votes to delete this question. I suppose that's because it had 30 upvotes? Anyway, currently it has 7 undelete votes. Does it need 9 to undelete? – Gerry Myerson Jul 5 at 5:52

Undeleted, reopened

Please consider undeleting and reopening this post:

How does one prove the inequality $$1+|x|\le (1+|y|)(1+|x-y|)$$?

OP clearly indicated the context of his/her question: it is from a proof in Wolff's lecture notes on harmonic analysis.

[Added upon request: this post has also been edited into a (more) decent one.]

• If you edit a post significantly indicate so in the request. I have no problem with it by itself, but since such actions are quite frequently overlooked by observers it can lead to the false impression that a relatively decent post was deleted. – quid Jul 8 at 14:07

Undeleted

How to find $${\large\int}_1^\infty\frac{1-x+\ln x}{x \left(1+x^2\right) \ln^2 x} \mathrm dx$$?

This is not a trivial exercise and OP shows his/her thoughts that "Routine textbook methods for this complicated integral fail." It has several very well-written detailed answers with rather high number of upvotes.

• '[S]hows his/her thoughts that "Routine textbook methods for this complicated integral fail."' That's not relevant context. Most likely it's a constructed challenge and should have been declared as such. This type of post borders on a misuse of the site. The following comment at score 13 is relevant I feel like it's becoming a trend to ask questions about practically impossible integrals. – quid Jul 8 at 19:34
• You think "That's not relevant context." And this proposal focus particularly on undeleting the post. Considering THREE high-quality answers (4+31+40 upvotes) that already existed I find it ridiculous (yes, this is my rant) to delete this OLD post. If there is any misuse of this site at all, the deletion, in this particular case, IS misuse of the privilege of votes. [mod redacted] – Jack Jul 8 at 19:58
• Bringing up other users in this form is out-of-line, in general. In the specific case it's also highly misleading. (I removed it.) – quid Jul 8 at 20:24

Reopened

Please re-open this question which is put on hold:

Understanding De/Suspension $\Sigma^{-1}(\Sigma{X})\neq X$

It was said that "unclear what you're asking" and people do not know the def of de-suspension.

However, the suspension is introduced earlier in the cited question:

The suspension (topology) and elementary examples

While the desuspension is also quoted/linked to the Wikipedia (withe refs given by Wiki). I also include a new note: "The desuspension is arguably firstly introduced in the cited text mentioned in H. R. Margolis (1983). Spectra and the Steenrod Algebra. North-Holland. p. 454." And the ref cited.

Question: How do we define desuspension exactly? (Please see the comments below, people complain about the meanings of desuspension in Wikipedia is useless).

Are we able to have the desuspension acting on the topological space as the suspension does? Or do we only have the desuspension act on the spectra but not the space?

Reopened

Please consider reopening this. It was closed originally as missing context. The OP provided some context in the comment and I have added a little bit more. Hope it is okay now.

• Wow, this question was through reopen review queue already four times. It makes me wonder what is the record. – Martin Sleziak Sep 1 '18 at 1:04
• I think it just how difficult it is to reopen a post using only the review queue. @MartinSleziak – user99914 Sep 1 '18 at 13:00
• This one has 5 and is still closed. – user99914 Sep 1 '18 at 13:01

Reopened

Please consider reopening the question A functional equation of a matrix that is placed On Hold. I have added my attempt at the cracking the problem if the lack of it was the reason for placing it on hold. The question itself is technically perfectly sound.

• You should have just edited your previous answer, and not added another "answer." – Joel Reyes Noche Sep 25 '18 at 7:07
• @JoelReyesNoche: What do you mean? "Answer" to my question that I linked to? I did not post an answer to my own question. – Hans Sep 25 '18 at 8:18
• No, answer(s) on the present meta page, there should not be two for a single post on main. – Did Sep 25 '18 at 9:31
• I have removed the second post, since this one has been edited to indicate the reopening. I've also edited and deleted/undeleted, so whomever downvoted can undo their vote. – Asaf Karagila Sep 25 '18 at 9:56
• @AsafKaragila: Oh, sorry. I did not know the first request was posted as I remembered closing the page rather than posting the "answer" as I needed to leave in a hurry earlier. I posted the second request thinking that the first request was not posted. This is the first time I post in the meta question site. – Hans Sep 25 '18 at 10:59
• Why this post says "reopened" when the linked question is still on hold at the moment? – Martin Sleziak Sep 25 '18 at 12:31
• @Martin, seems to have been a mistake, which I have rectified. – Gerry Myerson Sep 25 '18 at 12:37
• The thing that is missing in the current version of the question, more than work, is the source of the problem. Why do we expect it is true in the first place? – Carl Mummert Sep 25 '18 at 19:32

Undeleted

The deleted answer for Show that there does not exist a unique stationary distribution. should be undeleted.

The question is about "existence of unique stationary measure", and the answer is concise and to-the-point.

"$$(1,0,0,...,0)$$ and $$(0,0,...0,1)$$ are two invariant distributions so uniqueness fails."

The existing answer shares the same idea with the deleted one, and it has passed a Low Quality Review.

(Edit: comment removed)

The deleted answer attracted an comment from a high-rep user during another Low Quality Review. However, by appealing to his/her tag score for the relevant tags (, , , , , etc) (and the contributing posts) and comparing them with those of the answerer, you'll have a better idea about their contributions to the site in those areas.

• Oddly, the deleted answer was deleted, not through review, but by its owner. – Gerry Myerson Oct 12 '18 at 11:51
• You could ping the author on another of his posts, but I generally oppose undeleting a self-deleted post. – user296602 Oct 12 '18 at 15:14
• The author has commented on the other answer, so he can be pinged there if necessary. This is an odd situation. – Arnaud D. Oct 12 '18 at 17:34
• Thanks for advice. I did ping the author. He can undelete this anytime he wishes. I ponder whether CRUDE is healthy, when some of its active users vote to delete short answers outside their familiar tags regardless of the quality of the answer. This isolated example shows that its malfunctioning in terms of quality control. – GNUSupporter 8964民主女神 地下教會 Oct 12 '18 at 20:35
• @GNUSupporter8964民主女神地下教會 This isolated example shows nothing about CRUDE, since the delete votes and the associated comment came from the review queue, and the answer was never mentioned in CRUDE. Besides, I'm not sure tag scores are necessarily an indicator of expertise : for example I have a low score in "integration" because I don't really like to compute integrals, but I still know the basics and I think I'm competent to judge the quality of reasonably simple answers on the topic. – Arnaud D. Oct 15 '18 at 12:11
• @ArnaudD. I see your points, but let me clarify my stance. 1. To be more precise, I would say that this post shows the influence of CRUDE participation on other posts (not listed on CRUDE). In a review queue, it's possible that one votes to close/delete within a few seconds. Given the amount of posts that they review every day (in/outside CRUDE), this example reminds us the adverse effect of their rare mistakes dispite their high reputation. 2. That's why I've added "contributing posts" inside the brackets. – GNUSupporter 8964民主女神 地下教會 Oct 15 '18 at 12:47
• If you read the posts instead of the scores, you'll find out the truth: a) there's no probability theory in his/her "probability theory" answers. These are mistagged (elementary) probability questions. b) His/her stochastic calculus tag score comes from a reference request question. By the way, he/she has removed his/her comment. – GNUSupporter 8964民主女神 地下教會 Oct 15 '18 at 12:52

Undeleted

I nominate Group algebra&algebra for undeletion so as to give the community enough time to judge this value of its answer, which is deleted due to the question asker's self-deletion.

Reopened

(This is to break this request post into two)

I would like, if it is possible, remove the labels close-hold for some of next of my recent post Convergence of $$\prod_{n=2}^\infty\left(1-\frac{1}{n^2}\right)^{i^n}$$, where $$i$$ is the imaginary unit

I think that the answers are very interesting and very good, and I think that the questions are in the standard of questions of MSE. Any case many thanks.

Please reopen The characteristic polynomial of $A$ is $x^n$ if and only if $\text{Tr}(A^i)=0$ for all $1\le i \le n$. due to the reasons listed in OP's comment. The first duplicate matches half of the question. The hypothesis of the second duplicate is different from the first one.

Reopened

Please undelete Generalization of the fundamental theorem of duality since the question asker has deleted his/her own question shortly after receiving an answer. This is an abuse of the system.

Undeleted and reopened

Please reopen Proving the greatest lower bound. because OP has self-deleted his/her own question after I've answered this question. This inhibits the community from viewing the question.

Reopened

Please consider reopening the following question:

Maclaurin Series Expansion of $\ln(1+\sin x)$

The details which were included afterwards contradict the reason of closure. Moreover they indicate that the OP has as fundamental erroneous understanding of the concept of a MacLaurin Series - and how to derive them -rather than the unwilligness of showing his own efforts. In my opinion the question should be reopened.

Reopened

Show that the order of an element g is well-defined

The issue and its resolution can be seen in the comments to the thread. A brief summary is: I and others didn't understand the question (possibly others influenced by me), but I understand it now. Its fine in its current form.

• @Brahadeesh How is it closed as a duplicate? I didn't see it when I clicked into the question... – YuiTo Cheng May 2 at 8:21
• @YuiToCheng Terribly sorry, I could swear I saw it was closed as a duplicate. I'm reverting my edit. Don't know how that happened. :/ I'll be more careful next time. – Brahadeesh May 2 at 8:24

Undeleted, redeleted, re-undeleted, reopened

Please consider reopening the following question:

O is a point in triangle ABC. OA, OB and OC are joined and produced to meet BC, AC and AB at D, E and F. Find the value of OD/AD+OE/BE+OF/CF.

OP clearly indicates his/her attempt in the post:

I took the special case when O is exactly in the centre of the triangle and got the answer $$1$$. But how can I prove it by taking the general case?

This is not a zero effort question.

• Question was not merely closed, but deleted. Now undeleted (but still closed). – Gerry Myerson Apr 27 at 0:26
• It seems to be redeleted. – Brahadeesh Apr 30 at 3:58
• It's worth noting that special cases provides is an effect way to prevent "no-clue questions". – GNUSupporter 8964民主女神 地下教會 Apr 30 at 15:42
• The real missing context is the source and motivation of the problem. – Carl Mummert Apr 30 at 18:50
• CRUDE: "What is the source of FLT?" Fermat: "myself" CRUDE: "What is the motivation of FLT?" Fermat: "for fun" – GNUSupporter 8964民主女神 地下教會 May 1 at 0:14
• @GNUSupporter8964民主女神地下教會 If you actually believe that this is the way that Fermat conceptualized his work, then I would suggest that you have a deeply flawed view of history. While the culture of mathematics was quite different in Fermat's time (e.g. methods were generally regarded as secrets), I am quite certain that he was more than capable of describing motivation for his work and the context into which it fit. Your caricature of Fermat does a disservice to your argument. – Xander Henderson May 2 at 13:36
• Q: Where's the proof of FLT? Fermat: I don't have enough space to write it. Do we have as much sense of humor as the French three centuries ago? – GNUSupporter 8964民主女神 地下教會 May 2 at 15:00
• @GNU sorry to be blunt, but that just does not add up at all. So much so that there just is no joke there even. For a start, the problem is not due to Fermat. The famous margin is that of a published book he was reading (Arithmetica by Diophantus, IIRC) that presented the problem. I am to lazy to check what exactly it is but it's a certainty that there was some context there. For example, that for $n=2$ there is an infinitude of solutions that can be parametrized. Second, and crucially, Fermat never published or even mentioned that 'note to self' (likely as he realized it was wrong). – quid May 2 at 18:11
• @quid Thanks for your math history lesson, but I supposed that's a classic joke whose truth value wouldn't be judged as on the main site. Looking back, that doesn't suit serious math historians. Another meta post might be needed to avoid extended discussion here. – GNUSupporter 8964民主女神 地下教會 May 2 at 19:06
• @GNU what exactly should have been funny? You tried to ridicule others. – quid May 2 at 20:17
• @quid Your question concerns a subjective feeling, so the response is personal, and clearly mine can't be carried to serious math historians, but the historic truth itself is not the main point. If you wish a more serious example, you may consider Ramanujan instead. – GNUSupporter 8964民主女神 地下教會 May 2 at 21:05
• @GNU well, whatever, it seems you did try ridicule others. You tried to make a joke at their expense. This is has little to do with subjective feelings. It's an observation. If your intent was a different one, then what was it exactly? Example of what? Do you want to present Ramanujan as a good example of mathematical communication? What the example maybe shows is that just because something is presented intransperently one should not dismiss it out of hand. However, it seems to me that Hardy and maybe others did try to get Ramnujan to be more transparent. So what again is your point? – quid May 2 at 21:23
• @quid My "joke" is an response to Carl Mummert's comment. It's actually much more simpler than you think. Good math questions can come without source and motivation (comprehensible to others). If asked for a "motivation" and "source" for one of Ramanujan's identities (perhaps by Carl Mummert), what would Ramanujan respond? – GNUSupporter 8964民主女神 地下教會 May 2 at 21:36
• Quoting from Ramanujan's wiki page: "An equation for me has no meaning," he once said, "unless it expresses a thought of God." From this, a sensible response for Ramanujan would be an appeal to his own religious beliefs. From your comment to one of my recent meta answer, he wouldn't need to post the religious motivation on the main site. – GNUSupporter 8964民主女神 地下教會 May 2 at 21:45
• @quid I was typing on mobile, and my question "what would Ramanujan respond?" is intended to be answered in the reponse that follows. Many main site questions ask for proofs for an equation/inequality. Which particular identity is not important. Anyone will do, say, Ramanujan's triple product identity. According to Carl Mummert, in order to qualify as a good question, Ramanujan would have to provide a "source" and a "motivation" of his own identity. As a result, he would have appealed to his God, but that's not what the community wanted. So a request for motivation can get sth illogical. – GNUSupporter 8964民主女神 地下教會 May 2 at 22:14

Undeleted, put on hold, deleted

Please undelete https://math.stackexchange.com/q/3209899/290189 since OP self-deleted her own post after receiving an answer. This is an abuse of the system.

• I undeleted it. Please try to use correct terminology. Undelete and reopen are not the same. – quid May 2 at 7:33
• @quid Thanks for your undeletion and reminder. I'll be aware of that next time. – GNUSupporter 8964民主女神 地下教會 May 2 at 11:49
• Question is currently on hold. – Gerry Myerson May 3 at 3:06
• @GerryMyerson Thanks for notification. Status updated. – GNUSupporter 8964民主女神 地下教會 May 3 at 6:52

Undeleted and closed as duplicate

Choose 2 good batteries out of 8 (4 bad 4 good) was deleted by its author, after an answer was posted. This is considered to be an abuse of the system.

Full disclosure: the only answer posted before the self-deletion was mine.

• Currently closed as a duplicate. – Gerry Myerson May 3 at 3:07

Undeleted

Please undelete A probability to 6 in a dice since OP has self-deleted his/her own question after receiving an answer. This isn't fair to the answerer because his answer deserves review from the community.

Please undelete A contradiction in calculating the legendre symbol and https://math.stackexchange.com/q/3224172/290189 because OP's have self-deleted their question after receiving an answer from others.

• I undelete both. At least for the one, it'd also have been possible to let it deleted as it was a relatively simply oversight. It's not clear there is any value in keeping that around. But there is also no harm, so. – quid May 14 at 15:31
• Please adhere to the "one request per answer" format; having multiple requests in the same answer makes it difficult to track changes. – Brahadeesh May 15 at 8:03
• @Brahadeesh Thanks for your comments. I'll beware of this practice next time. – GNUSupporter 8964民主女神 地下教會 May 15 at 9:00

Undeleted.

Please undelete Bounding the number of edges in a graph satisfying a certain property since the question asker has self-deleted his/her question after receiving an answer.

## protected by Community♦Oct 1 '18 at 14:49

Thank you for your interest in this question. Because it has attracted low-quality or spam answers that had to be removed, posting an answer now requires 10 reputation on this site (the association bonus does not count).