# 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:

Reopened

Please consider reopening Minimal surfaces under conformal parametrizations - proof verification

It appears to have been closed after the user vandalised their question (rolling back the question would seem like the better approach, which I've done) and appears to have plenty of context and be a reasonable question asking for help.

Reopened

Prove $\lim_{z \rightarrow z_o} f(z) \in \mathbb{C}$ if $\lim_{z \rightarrow z_o} (z-z_0) f(z) = 0$

I made a new question, where I tried to be as clear and narrow as possible.

Reopened

There have been at least five questions asking how to prove instances of the general proposition $$\log_m(m + 1) > \log_n(n + 1)$$ for integers $$n > m > 1$$:

1. How to know if $$\log_78 > \log_89$$ without using a calculator? (3 May 2012), with an exemplary answer by user22805.

There have been at least three other questions asking to prove inequalities of the form $$\log_a{b} > \log_c{d}$$ for integers $$b > a > 1$$ and $$d > c > 1$$:

There has also been at least one more complex question in the same broad category:

Most recently, the following question was posted, but it was quickly closed as a duplicate (I confess to being one of those who voted to close it):

10. Comparing logarithms with different bases (23 Oct 2018).

The close message for question 10 reads:

This question already has an answer here: How to compare logarithms $$\log_4 5$$ and $$\log_5 6$$? 6 answers

But the only method used to answer a previous question (1-9) that can also be applied to the present question (10) is to find positive integers $$m, n$$ such that $$b^n > a^m$$ and $$d^n < c^m$$ (as in Eudoxus's theory of proportion), so that $$\log_ab > \tfrac{m}{n} > \log_cd$$.

In a comment (which has now been incorporated into the text of the question), the questioner showed that he was aware of this method, and had already used it to answer his own question. He continues:

However, that method doesn't work for every example, and I wonder if there's a easier way to solve this?

Strictly speaking, any logarithm comparison question could be answered in this way. But that is not always very practical, because one one has to search for suitable values of $$m$$ and $$n$$, which may be quite large. Some previous answers state or imply the general rule that $$\log_a{b} > \log_c{d}$$ if $$\tfrac{b}{a} > \tfrac{d}{c}$$ and $$a < b$$, but that rule does not apply in this case. It is interesting to ask if some other rule might be applied, eliminating the need for a possibly haphazard search for $$m, n$$. Failing that, ad hoc solutions to the present problem are also of interest.

Question 10 meets MSE's selection criteria, so it ought to be reopened.

• The question lacks contract in any event. Most importantly: why were the specific constamts in the problems chosen? If the problem is about arbitrary constants, it should be rewritten to say so. If the OP was already aware of a method to solve the problem, that context should also be in the post. Overall the post does.noy seem to demonstrate much effort to write a good post. – Carl Mummert Oct 28 '18 at 16:19
• @Carl On that basis, Diophantus would have a hard time posting a question here! Where, in MSE's rules, does it say that every question must be framed in the most general terms possible? What is wrong with asking a question about particular numbers? Especially as no-one has (yet) posted a general answer or a general question covering this particular case. Finally, even if it were granted (purely for the sake of argument) that an experienced user ought to have asked a more elaborate question, shouldn't a new user be cut some slack? – Calum Gilhooley Oct 28 '18 at 16:28
• @Carl Also, it was closed as duplicate, and my point is that it is not a duplicate. The close message is a false statement, and the close decision should be reversed. (Of course, anyone can also vote to close it for another reason, and no such person need feel obliged to vote for reopening.) – Calum Gilhooley Oct 28 '18 at 16:34
• !Calum: there's no problem posting a question with specific numbers - but it is up to the OP to include adequate context, and the reason for choosing seemingly arbitrary numbers is (in my opinion) part of that context. If this was asked person to person at a department tea, we would expect the asker to say something about the numbers involved. The OP should be encouraged to improve the problem, they have plenty of "slack" to do so. – Carl Mummert Oct 28 '18 at 21:19
• I think my guilty conscience over this has now been assuaged. :) – Calum Gilhooley Oct 29 '18 at 0:36

Deleted by a moderator

This question was closed and deleted with the reason given "This question is missing context or other detail". However the author of the question explained both his educational background (he is an undergraduate) and his motivation for the question (it was information that wasn't covered in his degree).

This information is sufficient context to give an answer, indeed I can't think of any further context that a person asking the question could add that would result in a better answer.

• The body does not even contain the question. That question-post is poor, and the thread of very limited value overall. The answers being pretty terse and not giving enough detail. // Added: Given the comment below I'll add that it was not I that deleted it. – quid May 9 at 6:59
• As far as I can tell, if a post was deleted by a moderator - like in this case - the deletion cannot be reversed by regular users. (Of course, voting your posts still can show to which extent users support undeletion - and if there is some support, perhaps moderators might have a look at the the question again.) – Martin Sleziak May 9 at 6:59
• @quid can you explain what is poor about the question? Broadly speaking pen and paper methods of factoring numbers is a subject that the site should have coverage of. – Q the Platypus May 9 at 23:32
• I already mentioned one shortcoming. Further and more drastically, the question does not contain any relevant thought of the OP or even just explanation what they want that information for. For example, do they realize that one can easily recognize that some number are not prime? How would they approach the problem for two digit numbers? Or something else, would all make the question better. That said, the question would arguably be saveable. But what for? The answers are low quality. I'd prefer somebody, say my students, won't find any information here rather than those answers. – quid May 10 at 9:55
• Fortunately similar information is available in other and better threads. In my opinion, the site is quite simply better without this thread. – quid May 10 at 9:57

Undeleted, reopened

Please consider undeleting this old post: Show that a function $$f:P(X)\to P(X)$$ preserving the subset relation has a fixed point

It was created on Sep 17 '16, has two good answers.

• It seems to be a special case of this question, and Aloizio's anwer in fact answers the general question. So if the goal is to preserve answers, the logical thing to do would be to move them there. – Arnaud D. Jun 28 at 13:48
• It seems to me the Question at issue here has the more general formulation (it does not require an "increasing" function). In any case I've voted to reopen as the Question at issue meets my threshold for context (and it otherwise also on-topic). – hardmath Jun 30 at 19:45
• I disagree with your assertion that the question has two good answers. It has one good answer, and a hint. The question itself is not good at all. I am content to see the question left undeleted, but I see no reason to reopen it. Arnaud D.'s suggestion is, I think, preferable. – Xander Henderson Jun 30 at 23:51
• "I am content to see the question left undeleted." Well, that is what my proposal is. I agree that the question itself was not good enough and thus I did not ask for reopening. @Martin Sleziak has added useful information to the post. (Thanks!) Also, Aloizio's good answer mentions at the beginning "the nice answer by @Brian". – Jack Jul 1 at 1:47

Undeleted, deleted, undeleted, reopened

Please consider undeleting this post: What is the formula of this angle?

There is a well written and well-received answer to this interesting question.

Undeleted, deleted, undeleted

Please undelete and consider reopening this post: Show this equation has every positive integer as solutions

OP did give his thoughts. NOT a no-context question. And there are two good answers.

Undeleted, deleted, undeleted

Please consider undeleting this post: How to evaluate $$\lim_{x \to 3} (x^2-5x+4)^{x-3}$$, which is clearly not a zero-effort question.

• You say that the question should be opened because it is "clearly not a zero-effort question." This seems to imply that the question was closed because it "lacks effort". However, "lacks effort" is not one of the close reasons used on MSE. Indeed, I see that question was closed for "lacking context". For example, a description of what theory the asker is familiar with and what course they are taking. Are they expecting a computation involving $\varepsilon$s and $\delta$s? L'Hospital's rule? What? The question should be deleted. – Xander Henderson Aug 15 at 12:31
• Moreover, examining the comments attached to that question, it is not even clear where the function being discussed is meant to be defined. Is it a real function with a very "hole-y" domain? or a complex function, in which case one needs to consider branches of the logarithm? It is not a good question. – Xander Henderson Aug 15 at 12:34

Please consider undeleting and reopening this elementary question: On proving $$\sum_{k=1}^{2^n+1} \frac{1}{k} > \frac{n}{2}$$

OP had his/her thoughts on the problem and also added an attempt for verification in the post after interaction in comments with others. This question has also been edited.

• Did you check to see whether it's a duplicate? Looks to me like the kind of question that would have been asked before. – Gerry Myerson Aug 23 at 12:20
• @GerryMyerson: I can only find a similar one. Since I have a very narrow definition of duplicate, I don't consider it as a duplicate to the mentioned one. Others may probably find closer one. One may close it as a duplicate if one does find one. But I would object the strong action of deletion of this post. – Jack Aug 23 at 18:02
• Asker account deleted, answer a brief hint, the argument definitely on the site numerous times, the specific variant a bit artificial. Why in the world should we keep that? – quid Aug 23 at 21:08
• @quid Why the account deleted is a 'point to count' to support the deletion? – Isabella Aug 23 at 21:59
• @Isa sometimes arguments are made along the lines of: "Maybe the post is not great, but OP made an effort and we should not discourage them via deletion." There are also glimpses of that in this meta post. Once the account is gone that caries rather less wait. Differently, it's not so much that it's a point for deletion, but it's a point less against deletion. – quid Aug 23 at 22:08
• @quid I don't get it. Your previous comment suggested like 4 'bad' things about the post, so why to keep that. – Isabella Aug 23 at 22:21
• @Isa I asked why we would want to keep the post. A common argument given is that we keep it not to penalize the person that asked it. This argument does not really apply in this case. Another argument is that the answer is good; Again does not apply. Still another argument we keep it for others users. But it seems unlikely to be useful, as the argument in principle is on the site numerous times and the specific version is a bit strange in a non interesting way. Thus, I still am at a loss why anyone would bother to keep that particular post. Surely there are plenty of better deleted posts. – quid Aug 23 at 22:30
• @quid I may agree with you the day I had 10k :) with your mentioned points: answer a brief hint, the argument definitely on the site numerous times, the specific variant a bit artificial. Except your first point: account deleted. I don't see any possibility of me agreeing with that point. – Isabella Aug 23 at 23:02
• Not exactly the same, but the question seems rather close to Prove this inequality: $\frac n2 \le \frac{1}{1}+\frac{1}{2}+\frac{1}{3}+...+\frac1{2^n - 1} \le n$. However, it's not suitable for merging - the bounds for sum are different, the other post has an answer rather similar to the one already posted. – Martin Sleziak Aug 29 at 6:58

Undeleted, deleted, undeleted, deleted, undeleted

I nominate Optimization problem for routes for undeletion because the question asker self-deleted his question shortly after receiving an answer.

Undeleted, reopened

Please undelete and reopen this post: Evaluate this limit: $$\lim_{n \rightarrow \infty} \frac{n\sin n}{2n^2 - 1}$$

This post is by no means missing context. OP clearly stated at the beginning what he/she tried and where he/she got stuck. This post has also a detailed answer by a 50K+ user.

• It might be worth noting that unfortunately that so-called detailed answer completely ignores the provided context, in that sense it's a rather poor answer, but arguably that's tangential. I'd tend to agree that this question does show reasonable context. If we take the context into account, likely it's a dupe. – quid Sep 23 at 15:52
• Instead of saying "what goes wrong with my thoughts" or "how can I go on with my original approach", OP explicitly stated that "Any help will be appreciated". And @Clement C. helped this user by directly giving an argument. Not a poor answer, and there have four people considering it good. This post is an extremely poor choice for deletion. – Jack Sep 23 at 15:58
• quid does make a fair point that an answer showing how OP could go on with the original approach may be more useful for the asker. One could add such an answer after this post is reopened. – Jack Sep 23 at 16:06
• Are you trying to make a point that because somebody collected 50k+ points by violating site policies and doing others homework for them, then that gives their opinion added weight somehow? I guess selling dung to horseflies is a lucrative business, but it does not make a good math site. – Jyrki Lahtonen Sep 30 at 4:56

Undeleted, deleted, undeleted, reopened, closed as duplicate, deleted, undeleted, deleted, undeleted

Please consider to undelete this question.

The OP brings some background about the problem and is just trying to find an easy solution. The one provided by me looks quite unknown (as it seems from the comments and the answers) thus I think it can be of future help if the question is undeleted.

• It's good form to disclose that one has an answer on the post oneself. – quid Aug 15 at 21:00
• This question is a duplicate of many other questions on MSE. While I don't think that it is worth keeping (it brings nothing new to the table), if it is going to be kept, it should be closed as a duplicate. I left comments indicating a couple of potential dupe targets. – Xander Henderson Aug 17 at 15:05
• On the contrary I believe it brings something new to the table. My solution is different than any other from all the linked posts. – Nyssa Aug 19 at 20:24
• @Zacky In that case your answer will stand its ground as an answer to the duplicate target as well, and you might consider relocating it there! Just by posting a new answer, the thread of your choice will be bumped to the front page, meaning that many viewers will see it and be able to vote it. <- This could be my template reply to all the users who are sad about a deletion of a duplicate. They can easily save their work this way! – Jyrki Lahtonen Aug 30 at 18:19
• "Partial fraction without defraction for an integral" What the heck does that mean? Is defraction really a word? Why has no one edited that title to something intelligible? – Gerry Myerson Aug 30 at 23:00
• @GerryMyerson I think that no one had edited the title into something intelligible because no one actually knows what the asker intended. That is part of the problem with the question (aside from the fact that it is a duplicate). – Xander Henderson Aug 31 at 14:17
• @Zacky Honestly, I think that Jyrki's advice is good advice. Indeed, I think that your answer would be a better fit for one of the other questions, if for no other reason than the current question specifically asks about partial fraction decomposition, while the others don't. Your answer would be a better fit for a different question. – Xander Henderson Aug 31 at 14:18
• @XanderHenderson something looks off. You said that it brings nothing new to the table and it's not worth to be kept, you even ranted on how my answer isn't a "pedagogical". Are you sure that you honestly believe that is a good advice? – Nyssa Sep 1 at 8:52
• I also wrote in my pre-edit for OP: "Since this is just for your training, here's a more different approach for it. If it doesn't fit for you, I will delete it (it doesn't use any partial fractions)", when OP commented I think I received a positive feedback about it from OP.// Indeed it doesn't answer the exact question, but another answer (which got accepted by OP) shows a way with partial fractions. I only posted my answer after I saw it, and after the comments (from some high-rep users) who encouraged OP to not look for a better way? – Nyssa Sep 1 at 8:58

Reopened

Please consider reopening Indian Mathematicians. The question was closed as off-topic, apparently because of the existence of the History of Science and Mathematics site.

As I pointed out in a comment, first, questions about history of mathematics are on-topic here. The tag has almost two thousand questions and a decent amount of recent activity.

Second, the quality of many interactions at the HSM site is sadly rather poor (I was very enthusiastic about it when it started, so this poor quality quite bothers me), and it may end up being a disservice to send this question there.

(I would actually love to see the quality at that site to raise uniformly, and hope it happens relatively soon. But that is another matter.)

• I think at least the formulation of the question should be clarified a bit before it is reopened. The first answerer already misunderstood it. – quid Aug 30 '18 at 21:11
• Fair enough. I'll do a slight edit. – Andrés E. Caicedo Aug 30 '18 at 21:16
• I had decided to do an edit myself. Sorry for the confusion. I'll check back in one or two hours. If it's still closed then I'll give the final vote(s). This allows also for further editing. – quid Aug 30 '18 at 21:19
• No problem. I gave the edit a second pass. (And thank you.) – Andrés E. Caicedo Aug 30 '18 at 21:22

Undeleted, deleted, undeleted, deleted, undeleted, reopened, closed, locked, unlocked, deleted, undeleted, locked (for historical significance).

I think this question should be reopened. Thank you!

The original poster looked for the possibility to use the substitution $$t=\tan\frac{x}{2}$$ and he got a number of solutions.

By the way, the first comment of Lord Shark the Unknown is nothing. At the least, it gives a very complicated solution which the topic starter tried to apply but without success.

• Quote from the question: "I tried tangent half-angle substitution but it became too complicated." First comment on main: "Try half-angle substitution, but with a little more determination. – Lord Shark the Unknown Aug 9 at 9:54" Answer by the OP: [DNE]. – Did Sep 8 '18 at 22:17
• "By the way, the first comment of Lord Shark the Unknown it's nothing" Pfff... – Did Sep 8 '18 at 22:44
• And now there's a rollback war. – Gerry Myerson Oct 1 '18 at 12:35
• This question feels like a joke that everyone gets but me. (1) Why is this question particularly bad? The OP said they tried the obvious thing but to no avail. Presumably they made a mistake, but so what? That doesn't invalidate the question. (2) Why is there such a fierce edit/close/delete war? The question is 2 months old - let it rest!!! – user1729 Oct 12 '18 at 17:11
• Rollback to Revision 9 by Alex Francisco, rollback to revision 10 by Michael Rozenberg, rollback to 9 by Alex, back to 12 by Michael, to 9 by Alex, to 14 by Michael, to 9 by Alex, to 16 by Michael. Crazy! – Gerry Myerson Oct 15 '18 at 22:44
• This is just sorta embarrassing to watch at this point. And it's already back to 2 undelete votes, so I expect another full cycle in the next day. – user296602 Nov 27 '18 at 18:28

Undeleted, reopened

I humbly request undeletion and reopening of this question, if you see fit to do so, because

a) reasons for closing should be derived from the question itself and not from speculation about the skills of the asker.

b) the given reasons for closing are incorrect - while the question sails close to an open problem, it asks a different but related question - it asks if the open problem (which relates to a series of polynomials) can be extended to its limit point.

c) the time from entering the reopen queue to deletion was less than two hours, denying any who might have been interested in its reopening the opportunity to declare the same.

d) moreover, I think others will find the question and any prospective answers of interest and value.

• The time from entering the reopen queue to deletion may have been short, but the question had been on hold for five days already. As for the close reasons, I'll note that 2 of the close voters did not use "not math". I think that personnally I would have probably voted to close as unclear what you're asking, because on a first reading I honestly had no idea what you were talking about. – Arnaud D. Dec 1 '18 at 12:43
• @ArnaudD. Yes, but the reopen request followed an edit which increased focus on the actual question and removed the motivation for it, when I believe the question's motivation was almost certainly the cause for the down votes and closure in the first place, rather than the question itself which stands alone. – samerivertwice Dec 1 '18 at 12:47
• By the way, I think the most recent edit on your question (post-deletion) already makes the question more interesting. It only consists of adding a Wikipedia link, but that link already explains some of the context better than your question (for example, I hadn't realized that you were talking about polynomial bijections $\mathbb{N}^k \to\mathbb{N}$, but maybe that's just me). – Arnaud D. Dec 1 '18 at 12:57
• For what it's worth, the reopen review was completed before the deletion, as one can see here. – Arnaud D. Dec 1 '18 at 13:15
• @ArnaudD. good point, although predominantly the same users. Is there a better review link that shows timings etc.? I thought I saw one before but can never re-find it. – samerivertwice Dec 1 '18 at 13:39
• There's the timeline, but I don't know if it is as detailed as you'd want. (By the way, there's another question about how to find it). – Arnaud D. Dec 1 '18 at 13:44
• Setting aside all other issues, there are some obvious (and, I think, easily correctible) errors in your question's key equation, stating the F-P conjecture: the right hand side has no $y$ in it, and the index of summation $n$ appears nowhere in the expression being summed. I'm pretty sure you want the summation to go from $k=1$ to $n$, not $n=1$ to $k$, with $f_n(x_1,\ldots,x_n)$ on the left hand side, not $f_k(y)$. – Barry Cipra Dec 1 '18 at 15:28
• @BarryCipra thank-you. I think I intended $y$ to be the set $\{x_1,x_2,\ldots x_k\}$ and yes, I agree I appear to have exchanged an $n$ with a $k$ but alas no edits are allowed on a deleted post so I can't correct it :( – samerivertwice Dec 1 '18 at 18:17
• @RobertFrost That's surprising. In any case, I've just done the correction. – Arnaud D. Dec 1 '18 at 18:57
• @ArnaudD. Thanks and you even got the $f_n$ I thought might get missed. – samerivertwice Dec 1 '18 at 19:00
• What do you mean by "timings"? The time of the review is there exactly. As usual, hover over the time stamp to get a resolution to the second. – quid Dec 1 '18 at 23:44
• @quid thank-you. That probably covers it although I can only see a deleted post on desktop so I'll have to check later – samerivertwice Dec 2 '18 at 4:07
• @ArnaudD. Thank-you for the edit. A reopen vote would be greatly appreciated (only if you think it appropriate). Else the deleters will reverse the undeleters! – samerivertwice Dec 3 '18 at 10:39

Can this answer (on permutation groups) be undeleted:

https://math.stackexchange.com/a/3197094/10513

It was deleted for not providing an answer to the question. However, it gives a decent hint which leads to a solution. The hint is essentially "consider odd vs. even numbers". This was made formal in the accepted answer, which used mod 2.

• I think it's a bit of a stretch from that hint to the accepted answer. The hint ought to be a comment (in my opinion). – Gerry Myerson Apr 29 at 12:50
• @GerryMyerson Hints are a grey area. But I don't think deleting them because they are "a bit of a stretch" is the right thing to do. – user1729 Apr 29 at 12:55
• It would have been better, had a moderator converted the "answer" to a comment. You could try flagging the question for moderator attention, and making that suggestion. – Gerry Myerson Apr 29 at 12:59
• I flagged it beforehand, and was told to post my request here (admittedly i didn't suggest making it into a comment) – user1729 Apr 29 at 13:19
• OK, now you know what to do. – Gerry Myerson Apr 29 at 13:22

Undeleted, Merged and then deleted

Please reopen https://math.stackexchange.com/q/3208119/290189 since OP has self-deleted his/her own post after getting an answer. The community should have been given enough time to vote.

• You can't reopen a question that isn't closed, GNU. Now it has been closed, as a duplicate, but I don't see how $x^y+y^x=(xy)^2-19$ is a duplicate of $x^y-y^x=xy^2-19$. So, I'm flagging for moderator attention. – Gerry Myerson Apr 30 at 13:47
• @GerryMyerson By the moment I posted this answer, I did voted to close this question as missing context. I did notice the difference between the two. Thanks for reminding me. – GNUSupporter 8964民主女神 地下教會 Apr 30 at 13:52
• @GerryMyerson a problem is that the original version of the question was incorrect. A third party edited it to this version, while main OP had re-asked a different version. – quid Apr 30 at 15:32
• I deleted it after the merge now. This did not work out ideally, but it's near impossible to fix. If somebody wants that version of the question on the site I recommend to ask it anew. – quid May 2 at 18:17

Please unmark the duplicate of this question. I have clearly said that my question has nothing to do with duplicate one. I am asking totally different thing and the duplicate question's answer does not help me at all. It is also an unique question which follows m previous question.

• I don't believe the relationship between the Questions is quite so simple as one "has nothing to do with" the other. Both involve intersections between two spherical caps, although you might not have visualized your problem in this way. There might still be a further problem in stating the area in terms of how you parameterized the spherical region, I grant, but it would be worth understanding the solution of the proposed duplicate to try restating the area given there in your terms. – hardmath Jun 6 at 17:11

Undeleted, closed, deleted, undeleted, redeleted

I nominate Solve the recurrence $$\sqrt {x_n} − 5 \sqrt {x _{n−1} }+ 6\sqrt {x_{n−2}} = 0$$ for undeletion because OP has self-deleted his post shortly after receiving an answer. That's rude to the answerer.

• I agree that the question should not have been deleted by the original asker, and would have voted to undelete had I seen this before the question was undeleted. That being said, it is a pretty low quality question, and would like to now nominate it for closure and (if it is not improved) eventual deletion. – Xander Henderson Nov 12 '18 at 23:26
• @XanderHenderson Agreed and updated the status of my answer. – GNUSupporter 8964民主女神 地下教會 Nov 13 '18 at 1:27
• It is inconceivable this question is undeleted. Even the answer is pretty low-quality. – YuiTo Cheng Jun 26 at 4:53
• I find that revision history really surprising : one (now removed) user voted to undelete and then close the question, OP initially self-deleted the question but 5 days later voted to undelete after the second deletion, and now you've voted to undelete and then redelete the day after. Pardon my French, but WTF? – Arnaud D. Jun 27 at 9:31

Undeleted, reopened

Please consider undeleting and reopening this post:

where OP gave his/her thoughts:

Honestly I have no idea about how to approach this problem. I tried the expansion of $$\sin x$$ on the left hand side and then expand $$\cos x$$ on the right but end up with a mess. Then again $$\cos x=(\sin x)'$$, but by converting each term on the right hand side into derivative of sine does not give any sensible identity to draw out something. Really out of ideas on this one. Is there any way to do this? Please give me some hints. Thanks for your time.

Undeleted, deleted, undeleted, reopened, closed as duplicate (mod)

Please consider undeleting this post: 2011 IMC Section A Problem 3

This is not an ongoing contest problem. The answer is known online. @Aqua's answer (with 14 net upvotes) is a useful one.

• Poorly explained answer. Had downvoted it back then. – quid Jul 6 at 19:53
• That was a really bad excuse for deletion. – Jack Jul 6 at 21:09
• Since I did not delete it, I don't need any excuse (and I doubt the delete-voters where aware of my voting back then). Please do not write comments that might suggest otherwise as not everybody can check it easily. – quid Jul 6 at 22:20

Undeleted, deleted, undeleted, deleted, undeleted, reopened

Please consider casting the final undelete vote and reopening this post:
Evaluate $$1+2-3-4+5+6-7-8+\cdots+50.$$

This question is well written and with effort. It has very well written answers, one of which gives a generalization of the problem.

Reopened, undeleted, closed

Please consider undeleting this question where I also provided an answer: Integrating $$\int_0^1\frac{x\ln (1+x)}{1+x^2}dx$$ with restricted techniques.

The OP from clearly provides background on how the integral appeared, although it was some kind of homework now it can be useful for others too.

• It's good form to disclose that one has an answer on the post oneself. – quid Aug 15 at 20:59
• Hope I don't sound rude, but I don't understand what you wrote even with translate. Did you meant: It's a good thing to mention that I posted an answer to the linked question? – Nyssa Aug 15 at 21:07
• Yes. You should mention this. It makes clear that you are not a neutral third party. You have a personal interest in the undeletion. This does not disqualify you from making the proposal. But it is good form to be upfront about it. – quid Aug 15 at 21:12

Deleted, undeleted, deleted, undeleted, reopened, closed as duplicate

Please reopen Calculating the summation$$\sum_{n=1}^{\infty}\frac{H_{n+1}}{n(n+1)}$$ because it's not an elementary question and OP has tried checking the proposition using Wolfram Alpha.

• In my opinion it's very poor style to reignite this after month without mentioning any of the earlier activity in which you even were involved. Thus, I locked the post for now. – quid Apr 30 at 11:43
• I'm puzzled. A "content dispute" notice was lifted in March 2018. The content has not been altered since then. So it seems strange to lock it for "content dispute" now, @quid. [I guess I should mention that I was involved in earlier activity.] – Gerry Myerson Apr 30 at 13:56
• @GerryMyerson Are your really puzzled or are you just searching an argument? First, the content of the post was also not changed between the first locking and the first unlocking. Second, the lock was not lifted in the sense of somebody lifting it, it simply expired. It was not reinstated as there seemed no need back then about a year ago. Then half a year ago, there was one more round of undelete-delete but it fizzled out quickly. Now somebody wants to go back to this again, indeed without any further changes, simply picking up the del-undel again. To prevent this, I locked it. – quid Apr 30 at 14:36
• Third, it might be relevant to note that the lock was "lifted" while the post was deleted. Thus, if consistency is the concern of course I should lock it again now. I could also have it become undeleted and then personally delete it again. Last time around some where keen on locks being used. So, there you go. Of course that's not fine for you now either, presumably because it does not cater to your personal preferences. – quid Apr 30 at 14:43
• To sum up, I locked it to prevent the delete-undelete cycle being restarted. By now the question was deleted four times. Plus it is an odd situation, in that it first got siginificantly improved by a third party only for this then being undone If anything should happen likely a completely new version should be posted. This would be a reasonable thing to do if preserving content is the actual goal. Of course if playing un-del games should be the goal... thus locked. @GerryMyerson – quid Apr 30 at 14:48
• @quid, when I write that I am puzzled, please do me the courtesy of accepting that I really am puzzled. I'm puzzled not so much by the locking but by the phrase, "Content dispute", when there was no change in content. Had the locking notice said "Prevent delete/undelete cycle" I don't know that I would have made any comment. Does a moderator have the option of inserting custom-made locking notices, or is "Content dispute" the only phrase available? Also, I always assumed that when a moderator locked a question, the question stayed locked until a moderator decided it was time to unlock it.... – Gerry Myerson Apr 30 at 22:46
• ....I didn't know that locks expired of their own accord after a week. I've been here almost a decade, and I'm still learning how the place works. – Gerry Myerson Apr 30 at 22:47
• @GerryMyerson the list of reasons is fixed (we can ask for additions in principle but not spontaneously) "content dispute" is the one commonly used in this case, others are "off topic comments", "contest question", "cw answer", "historical significance". We can lock for an hour, for a day, for a week, or permanently. Usually one tries to avoid permanent locks. – quid Apr 30 at 23:58
• Probably it's worth mentioning that there already is one answer in this thread about the same question. – Martin Sleziak May 15 at 7:34
• @quid, thanks for the explanation about length of locks. It's not possible, is it, for non-moderators to see what length a moderator has chosen when that moderator locks a question? – Gerry Myerson May 20 at 4:26
• @GerryMyerson indeed I think that's not possible. – quid May 20 at 8:39

Undeleted, reopened

Please undelete and reopen this post:

How can one use the direct comparison test for $$S=\sum_{k=1}^{\infty}{\frac{1}{\sqrt{k}+10k}}$$?

Even in the very first version of the post, OP states his/her thoughts and difficulties he/she has. This post is NOT missing context. And it is NOT a duplicate of any other question.

• Because we already have many questions where divergence of a series is deduced from a comparison with the harmonic series, this is bound to be a duplicate dozens of times over. Therefore the question should also be closed as too localized (not adding anything new to the site, and only helping the asker do their homework). Missing context is the best proxy we currently have, so if reopened I will vote to reclose and redelete. – Jyrki Lahtonen Sep 30 at 4:53
• @JyrkiLahtonen Maybe I should have trie to search a bit more, but by a quick search I only found this: Calculus II: Comparison Test for Divergence $\sum\limits_{n=1}^{\infty}\frac{1}{n+\sqrt{n}}$. (All I am saying that I am unable to confirm that there are dozens of posts which are close to duplicates. Although I agree that when I saw the question, I expected that there should be many similar questions.) – Martin Sleziak Sep 30 at 8:09
• @MartinSleziak It is one of the standard series to use a comparison test with :-) Anyway, when the question is a (near-) duplicate IMO showing effort/thoughts is NOT SUFFICIENT to stop closure/deletion. The questions should have wider interest, and the context should demonstrate that. – Jyrki Lahtonen Sep 30 at 9:59
• Mathematics Stack Exchange is a question and answer site for people studying math at ANY level and professionals in related fields. How many questions a student asks are not supposed to be "standard"?! And is any one of the four mentioned in the first comment not standard? – Jack Sep 30 at 11:59
• @Jack Your comment about MSE being for questions at any level is a red herring---the question was not closed because of its level. The question is a standard question which occurs (in one form or another) in many elementary texts on calculus. Moreover, it is a question which already has an answer on MSE. What new, valuable information does this particular question add to MSE which isn't already on the site? – Xander Henderson Sep 30 at 20:18
• How many questions a student asks are not supposed to be "standard"?! @Jack, not very many. The same applies to StackOverflow. Which is exactly why Jeff Atwood wrote that a new asker should spend 98% of their time on StackExchange searching. Getting more and more questions does not improve the site, and is not necessary for its success any longer. On occasion it is quite the opposite. – Jyrki Lahtonen Oct 1 at 14:06

Undeleted, deleted, undeleted, reopened

Please undelete On a colon ideal in the polynomial ring $\mathbb R[x,y]$ because this question has got a score of 2 after OP included his/her own thoughts on the problem. This algebraic geometry question might add value to the main site.

• Selfdeleted without answer. No need to undelete. – quid Feb 25 at 9:16

Undeleted, redeleted, re-undeleted, redeleted, undeleted

Please consider undeleting the question: The asymptotic behavior of $$n\ln n -n$$

• Well, I'd consider something in the spirit of the comment as the best answer there. Anyway given the complete lack of context it's hard to know which type of answer would be useful, whence the voluminous list. Also all standard likely on the site in similar form tens if not hundreds of times. At least one answerer made the effort to link it to related posts. – quid Jun 6 at 22:37
• Redeleted (6/17/19) by a same group of users. One initiated three times the delete votes and one voted three times to delete this post. – Jack Jun 17 at 22:01
• Probably I should have refrained of posting an answer there - however at the time when I posted there were some answers already and they seemed (to me) more complicated than needed. I have also included links to some other questions - you can see that similar questions are on the site (and they have similar answers). I will also say that when posting the answer I was fully aware that the question is likely to be closed/deleted. – Martin Sleziak Jun 18 at 17:35
• @MartinSleziak: I believe "closing" is enough for this particular post. I strongly disagree with the deletion considering the high qualities of answers. Such good contents will be useful for future readers (this is closed post is not some stupid trivial textbook exercise) and should be preserved on the site. – Jack Jun 28 at 12:22
• @Jack Well, several discussions here on meta suggest that when deciding about closing (and probably also deleting), most users take into account mainly quality of the question (and do not look at answers). Since you have mentioned that you care about preserving context, I should specifically point out that my answer contains some links to other posts which use Stol-Cesaro. Will Jagy reposted his answer in another thread. (For obvious reasons, I might be a bit biased in this particular case.) – Martin Sleziak Jul 6 at 17:55

Please consider undeleting this post: Integral $$\int_{0}^{2\pi} \ln (2\sin(\frac{x}{2}))dx$$

Whether the asker should articulate more details in "I've tried some substitutions" could be debatable for reopening the post; I do not think it should be deleted. There have been two answers, one of which has 11 upvotes.

• The question was on hold for a week without modification before it was deleted. The answers are fine, but standard, and don't rise to the level of exceptional. I see no reason to undelete this question. The asker clearly got what they wanted, and I don't see that question providing any lasting value to the site. – Xander Henderson Jul 2 at 0:46
• The lasting value to the site, like many other posts, is that there are two good answers to a tricky calculus question, which is not only useful for the asker but also future readers. – Jack Jul 2 at 1:48
• The first part of your reply to me does not contradict what I said: you say that there are two good answers, I said that there are no exceptional answers. As to use to future readers: I disagree. This is a specific integral which can be analyzed using relatively standard techniques. The question itself is not terribly searchable (it is only going to come up if someone wants to deal with that specific integral (e.g. they are assigned the same problem as a homework exercise, and are trying to cheat), and the answers are not of any general interest (they are standard, but not general). – Xander Henderson Jul 2 at 1:53
• Disagree. "This is a specific integral which can be analyzed using relatively standard techniques. ... the answers are not of any general interest " does not justify the deletion. MSE is not MO: most, if not all, of questions here "can be analyzed using relatively standard techniques". For instance, this recent question that has two good answers, the accepted one written in detail nicely by you, is a rather "standard" one. I would certainly not vote to delete such posts. (In case of any possible confusion: this is NOT sarcasm.) – Jack Jul 2 at 2:48
• It is funny that you pick that example. I downvoted that question, and voted to close it. It was not closed, and the other answers were, in my opinion poor answers (as they failed to address the key point, which is that an induction proof is needed somewhere). If the question is not going to be closed and deleted, it should at least have a correct answer. I would still be happy to see that question closed, and would not object to its deletion---my answer is nothing special, and doesn't (IMO) rise to the level of exceptional. – Xander Henderson Jul 2 at 2:56
• Moreover, applying standard results to a specific problem is very different from demonstrating the correctness of standard results then leaving it to the reader to apply that result to their specific problem. – Xander Henderson Jul 2 at 3:01
• Well, (1) I have done my proposal for undeletion. Readers can make their own decisions. (2) I will object strongly the post I just mentioned being deleted, considering the quality of your exposition and egreg's good answer. (How do you find the review history by the way?) (3) ... have to leave now. – Jack Jul 2 at 3:13
• Probably a duplicate of one or more of math.stackexchange.com/questions/815762/… and math.stackexchange.com/questions/889902/… and math.stackexchange.com/questions/679233/… and math.stackexchange.com/questions/2656431/… and also comes up in any question containing the name "Clausen". – Gerry Myerson Jul 2 at 3:20
• @Jack To find the review history I go to the timeline of the post and then click on the link to the review event there. I don't know if there's a quicker way. – Brahadeesh Jul 2 at 6:41
• @GerryMyerson: having read your links one by one, I would probably not called the post a duplicate of those, although they are related to the Clausen function. (Never known this before, thanks for mentioning it.) – Jack Jul 2 at 11:47
• @Brahadeesh: Thanks for that. One can indeed use math.stackexchange.com/posts/3143084/timeline – Jack Jul 2 at 11:56
• It's funny how those who voted to close/ delete are here on this site for a while, and even claim to know that the question is easily searchable. Yet, instead of trying to mark it as duplicate, they simply delete it. Also it's quite bold for a single group of people (CRUDE users) to decide that it has no value for this site. – Nyssa Jul 22 at 8:50
• @Jack would you be interested to help, if a chat-room to counter CRUDE people's rampage to delete such questions would be created? – Nyssa Jul 22 at 8:51
• -> Before voting to delete, please check whether there are any good answers; if so, then the question should be flagged for moderator attention as a potential merge candidate. We don't like to lose great answers!. And the answers provided there are definetly good. Thus those who deleted it violated the "rule" that I copy-pasted. // A little off-topic, but I hope that you are aware that who asked the question couldn't care less if the question is deleted since he/she already took the informatio needed. Thus by deleting the question, it even helps that user instead of penalizing them. – Nyssa Jul 22 at 14:00
• -> Of course, the posts around here aren't only for those who asked, but for the whole community. I fail to see why there ins't a way to penalize the users (for example a "question ban" if the questions previously posted are bad), but instead the decision that CRUDE users took is to penalize the whole community by erasing good content. Anyway, it's pointless if I type here in the comments, soon I will try to make a meta post about something related to this. Thanks for your time and have a nice day! – Nyssa Jul 22 at 14:12

Undeleted

Please undeleting this post: How to prove that $$\frac{e-1}{2e} \le \int_0^1 \frac{e^{-x}}{1+x}dx \le \ln 2$$

OP did have his/her own attempt. This is not a zero-effort trivial question, which should not be deleted.

Please undelete this post: $$n^4 + 4^n$$ is a not a prime

OP clearly states context for his/her question:

This question appeared in the undergrad entrance exam of the Indian Statistical institute.

When $$n$$ is even the proof is simple. For $$𝑛=2𝑚+1$$ I am utterly stuck.

True that this is a duplicate of some previous posts, but duplicate can be useful. Moreover, it is not necessarily easy at all to identify this question as a duplicate:

• The useful searching engine Approach0 is NOT well known, neither it is mentioned on the page of help center of MSE.
• A quick search of the expression $$n^4+4^n$$ on the MSE searching box returns something irrelevant:
• If one posts this as a new question: the "similar questions" box does not show any one of the duplicate:

"Questions that are extremely off topic, or of very low quality, may be removed at the discretion of the community and moderators." This 5 upvoted one with three answers is not.

• At some point, every math student really ought to be shown the factorization of $x^4+4$. – Gerry Myerson Sep 26 at 7:47
• This is an umpteenth reincarnation. Even in 2013 when André Nicolas answered it we had already covered it many times. Also, while duplicates were seen as somewhat useful back in 2013 (when Jeff Atwood's strangedupe comment was often cited), the site has moved on since. The most recent word from above (don't remember for sure whether it is from JA or the current CEO Joel Spolsky) reads: Over time duplicates become vast landmine fields. – Jyrki Lahtonen Sep 26 at 16:24
• The sentence ("... landmine fields") Jyrki mentioned is from this article by Jeff Atwood. That one is specifically talk about StackOverflow, which is sort of the counterpart of MathOverflow. (cont.) – Jack Sep 26 at 17:18
• Jeff explicitly writes in that article the following : But I will point out that there is plenty of precedent on the Stack Exchange network for splitting sites into "expert" and "beginner" areas with slightly different rulesets. We've seen this for Math vs. MathOverflow, English vs. English Learners, Unix vs. Ubuntu... perhaps it's time for a more beginner focused Stack Overflow where duplicates are less frowned upon, and conversational rules are a bit more lenient? – Jack Sep 26 at 17:18
• I am not following SO much at all, but what little I have seen of it it is nowhere near the level of sophistication of MathOverflow (admittedly my observations are likely biased). But I would support walling off lower level math (like freshman and below) to a Math Learner site. – Jyrki Lahtonen Sep 26 at 21:49
• I don't get what's the contradiction even. Certainly duplicates will happen, some will be caught other won't be caught. Of those that do get caught we'll keep some that seems relevant as "sign posts" and we remove the rest without much ado (either way). Why would we want to keep them? – quid Sep 26 at 22:26
• On search, searching n^4 + 4^n for works like a charm Why would one use strange spacing, or in any case just check one version, and include the completely irrelevant dollars? – quid Sep 26 at 22:34
• @quid: your linked search of n^4 + 4^n , which does return a duplicate result, uses "strange spacing". If one searches n^4+4^n without the spacing before and after the plus sign, one would not see the charm. – Jack Sep 27 at 0:04
• The answers are all dupes of answers given many times in the past. This FAQ occurs many times every year. There is no need to keep adding duplicate answers every time it reoccurs. Doing so makes it difficult if not impossible for users to locate the most enlightening answers. – Bill Dubuque Sep 27 at 0:45
• @Jack I forgot to add that Theoretical Computer Science is the StackOverflow analogue of MathOverflow. Don't get mislead by the inclusion of the word Overflow. If SO walls off a learners' site, we should do the same. – Jyrki Lahtonen Sep 27 at 3:42
• And also, the voting already gives low level math an unhealthy advantage in the gamification aspects of the site. Simply because users are obviously not going to (and should not) vote on material over their head. You wanting to be more lenient about low level duplicates would exacerbate an already serious problem. – Jyrki Lahtonen Sep 27 at 3:45
• Well, let's forget about which spacing is strange or not. One might learn the lesson that one should search for both variations. I'd still maintain that the spacing there is the more natural way to type it. But I am glad that you seem to agree now that the dollars are useless. // And even if it was completely unnatural it is the very spacing that was used in that post that you want undel too. Thus at least that user likely would have used the same spacing if they had searched and keeping this as a dupe would not even help future searches (except maybe via answer, but then merge could do). – quid Sep 27 at 8:44

## 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).