# What's with these “sangaku” geometry problems?

This morning I decided to whip out my phone and check out some new questions on the main site through my mobile app. To my surprise, I saw 8 questions, titled or labelled as "sangaku" geometry problems, in a row on the front page. Furthermore, they were all edited $$2$$ hours ago. They were posted by different users across varying reps (so, unlikely to be one person behind different accounts). Most have a similar number of upvotes (~10). Can this be a coincidence?

• I reviewed (and accepted) the tag creation. The word sangaku is of Japanese origin according to its Wikipedia article. It seems worthwhile to me to learn something about this tradition. – hardmath Nov 23 '18 at 2:28
• I have pinged the tag-creator - so the at least they are aware of this post on meta. – Martin Sleziak Nov 23 '18 at 7:49
• @MartinSleziak Thank you for the notification. – Jean-Claude Arbaut Nov 23 '18 at 8:10
• Overkill on the editing, to add the tag to other posts, I'd say. Slow down, @Jean-ClaudeArbaut – amWhy Nov 23 '18 at 15:36
• I think (sangaku) is a fine tag to have here. But 8 edits in one day is far too much for an eager editor to do. – GEdgar Nov 24 '18 at 12:09
• Please edit a reference to sangaku into your question. – smci Dec 3 '18 at 17:56
• Also, 'sangaku' is a meta-tag about a problem/puzzle's cultural/historical origin, we do not have tags like 'vedic' or 'tangram', although we do have rubiks-cube. Should we ask more generally about cultural meta-tags? (and not this particular user's behavior in tagging?) I mean, we don't tag graph-theory questions "Seven-Bridges-of-Königsberg". – smci Dec 3 '18 at 17:58
• FYI, by analogy there are >>120 different genres of Japanese logic puzzles, just for constraint-satisfaction logic puzzles on nxn grid. We can certainly use those words in plain-text, but I wouldn't create a tag except where merited. Or maybe just a generic tag: 'japanese-logic-puzzles'. ('japanese-geometry-puzzles', etc.) – smci Dec 3 '18 at 18:05
• @smci Hey this question was solved 10 days ago, so your comments are useless. – Takahiro Waki Dec 3 '18 at 22:21
• @TakahiroWaki: no the comments are not at all 'useless', and no the general question wasn't 'solved'. Which meta-tags on which specific SE site are good/bad/approved/discouraged is very much a live topic. And 'your comments are useless' comes across as rude, even if it wasn't also incorrect, which it is. It would be good to get guidance on which meta-tags on Math.SE the community finds necessary. Hence my comments. – smci Dec 4 '18 at 0:05
• @smci Sorry. you misunderstand the question. This question doesn't argue about the sangaku tag. This question mention "What is this phenomenon?" . The rude comment is your three comments. – Takahiro Waki Dec 4 '18 at 5:30
• @TakahiroWaki no need to get worked up. The question was intended to ask for the explanation of the simple phenomenon, but if it's opened up discussion about the tagging system on MSE, thats a good thing as well! – YiFan Dec 4 '18 at 5:33
• @YiFan If so, yes. Here is wrong place about new discussion. – Takahiro Waki Dec 4 '18 at 5:38

A user created the tag then edited ten questions to include that tag, all in a short span of time. The user then created descriptions for that tag.

As has been pointed out in the comments below, some users consider very inappropriate the editing of many old questions in a very short span of time, and some consider very inappropriate the addition of a newly created tag to many questions without first seeking community input.

• Count me among those who view editing ten (old) questions in a short span of time as seriously inappropriate, as it drives newer questions off the front page even faster than usual. I thought mine was the consensus view here, the view generally taken concerning past editing sprees. – Gerry Myerson Nov 23 '18 at 6:24
• @GerryMyerson For more than one year the default tab on MSE has been the "interesting" tab. Because of this it doesn't really make sense to talk about the front page anymore: different users get sent different lists of questions on their front page depending on various factors (e.g., reputation, watched/ignored tags, answering habits). – fəˈnɛtɪk Nov 23 '18 at 6:40
• @1-3-7, is it the case that edits have no effect on what shows up on the "interesting" view of the front page? – Gerry Myerson Nov 23 '18 at 6:46
• @GerryMyerson Again, there is no more the front page (note the definite article). Different users have different front pages. Edits may affect a user's front page (depending on various factors, including many which are user-specific). Those same edits may have no affect on another user's front page. Even if the two users request their front page at exactly the same time. – fəˈnɛtɪk Nov 23 '18 at 7:06
• @GerryMyerson It all depends on what counts as short time span. (I wouldn't see a problem with 10 question bumped during 24 hours. But bumping 10 questions in 10 minutes is clearly too much. And I'd guess most people would draw the line somewhere in between.) In this specific instance I see as a bigger problem that many questions are given a newly created tag - if the community consensus is that the tag should be removed, we'll need to bump them again. There is an older thread related to this issue: ... – Martin Sleziak Nov 23 '18 at 7:39
• ... Limit for number of questions where tag can be added by tag-creator soon after the creation of tag And I will add also this link - also the thread is ancient and the site is now much much bigger then when the "allowed" amount of bumping was discussed a few years ago: How much bumping is too much? (In both cases there are a few related discussions among linked questions: math.meta.stackexchange.com/questions/linked/5068 and math.meta.stackexchange.com/questions/linked/27492 .) – Martin Sleziak Nov 23 '18 at 7:40
• Count me as someone who thinks that adding a new tag without any second opinions or explanation is seriously inappropriate. Also the edits, yes. But I agree that as a one-off behavior it isn't the worst thing one can do. – Asaf Karagila Nov 23 '18 at 7:55
• @AsafKaragila: That seems level-headed and reasonable given your views (which I find a bit strongly formulated), particularly as it is not obvious that a large number of tag additions will have undesirable effects – that seems to me to be a problem with the site. – PJTraill Nov 24 '18 at 13:45
• How the hell is anyone supposed to know that adding a new tag to a bunch of questions that clearly belong to the tag is a bad idea for any reason, but especially because of the side effect that those questions then get promoted on the main page? You could be a happy SE user for many years and still not know that! Think about it: Except for that side effect you wouldn't know about it, and if told you'd probably consider it an improvement to the quality of the Q&A portion of the site. Maybe it is the side effect that tagging a question moves it to the front page that is wrong! – davidbak Nov 26 '18 at 6:02
• I don't think I'm feeling it as strongly as davidbak, but count me as someone who's a bit mystified by the people (who I recognized as high-level and continuing contributors to the site) who find this inappropriate. I've been around here a while (2K rep whooo!) and had no idea of the etiquette surrounding tags. Admittedly don't really use the tag system much, and only did a bit of poking around to see what the tags interface was like - maybe there are warning signs there - but didn't find anything. And I could totally see myself doing exactly what JCArnaut did without .... – JonathanZ supports MonicaC Nov 30 '18 at 21:41
• ... the least suspicion that it would muck things up. So I guess this particular instance went okay but I think this is telling the admins that the policies surrounding tags are not very well communicated, and maybe be a bit more understanding about that. – JonathanZ supports MonicaC Nov 30 '18 at 21:45

I did this. Sorry if this was inapproriate. I know it's not a good idea to edit many questions in a short time span, but I thought 10 was acceptable.

With regard to the tag creation, however, I was not aware that it's inappropriate.

I'll take note of the various opinions expressed here, for the next time I have such an idea. Note that (I believe) it was my first tag creation.

Also, it may be worth telling it, even though you are not forced to trust me: I have one account, and I am not related to any of these questions. I didn't check but I believe I didn't post any answer nor comment anything in them (appart from a comment today about a dead link). If some have many upvotes, my guess would be that it's because they are visually appealing puzzles, related to a fascinating tradition.

• The tag itself is certainly a great idea, and you have done a service to the site by adding it :) – YiFan Nov 23 '18 at 8:18
• Putting aside the issue of unilateral tag creation for a moment, I do think it's a reasonable tag. – Alexander Gruber Nov 23 '18 at 8:44
• I will add a link to the previous discussion related to this: Should every new tag be discussed on meta before creation? The accepted answer says that it is not obligatory to ask on meta first. (Although not everybody agrees.) Still it would be polite after creation of a new tag to leave some time for the community - so that people can notice that a new tag was created and if they have objections, they can raise them on meta. (You can find here on meta some instances where over 50 questions were quickly added to a new tag before any discussion ... – Martin Sleziak Nov 23 '18 at 9:03
• ...and the tag was later removed.) This is most likely not going to be an issue in this specific case - so far the reaction here in this thread seems to be that most people consider it a useful tag. – Martin Sleziak Nov 23 '18 at 9:06
• IIRC the tag had existed for years as a synonym that hardly ever was used (which is why I removed it at some point). I don't think that tag is really useful, but at least as an actual tag it might have some use. – quid Nov 23 '18 at 13:31
• The tag is purely a religious concept. It has no business on a mathematical site. It needs to be nuked immediately. It does not define a branch of math. Sangaku is the act of offering theorems as a religious sacrifice based on the Wikipedia article. Many people will be offended by the site treating it as a mathematical subject. It might be taken that applying the tag makes the post itself a religious sacrifice. That has no place here in my opinion. – user64742 Nov 24 '18 at 0:41
• @TheGreatDuck I don't agree with you. There are mathematical books on sangakus. It does not necessarily convey a religous meaning. But if it's a pretext to remove the tag, then so be it. – Jean-Claude Arbaut Nov 24 '18 at 9:13
• Thanks for coming here to explain. Personally I would prefer that new tags should be "cleared" in meta before creating them. Partly for the reasons in Gerry Myerson's comment, partly because sometimes relative noobs do this misguidedly. In the case of this tag I do think that you would have had no trouble whatsoever getting that clearance. So no harm done (other than the edit spree - when judged necessary the preferred way is to space them out a bit). – Jyrki Lahtonen Nov 24 '18 at 10:57
• @JyrkiLahtonen Understood :) – Jean-Claude Arbaut Nov 24 '18 at 10:58
• @TheGreatDuck: Obviously questions purely about religion have no place here, but I welcome questions about the culture of mathematics, and if religion plays a rule, I see no problem. One the other hand, I think that sangaku should not be overemphasised if a problem is otherwise well-known. – PJTraill Nov 24 '18 at 13:52
• @TheGreatDuck - wut? I'm with Jean-Claude Arbaut - it's not a "religious" tag when applied to specific mathematical problems that share a common "theme" or "background", just because those specific mathematical problems might have been initially "published" as (allegedly) some form of religious offering. (And that isn't even clear at this date.) – davidbak Nov 26 '18 at 6:30
• @TheGreatDuck - I strongly disagree. – JonathanZ supports MonicaC Nov 30 '18 at 21:46
• @JonathanZ well my thinking was that if Sangaku is a religious activity then the existence of the tag might be viewable as sacrilege by people from that culture. Hence why I feel the tag shouldn't be used. – user64742 Dec 1 '18 at 6:20
• You've gone from "The tag is purely a religious concept .... it needs to be nuked" to "if Sangaku is a religious activity ... might be viewable ...". You probably should have researched it and brought some evidence that that was the case before asserting that as a claim. I know that as a Jewish person if I discovered through math.stackexchange some area of Judaism that had a mathematical connection I'd get a huge kick out of it. – JonathanZ supports MonicaC Dec 1 '18 at 17:16
• @JonathanZ: Hebrew gematria, Greek isopsephy, Arabic abjad numerals, English gematria are essentially the same concept, with different alphabets and letter-scores. But naming/aliasing one single name for all of those could get controversial... – smci Dec 3 '18 at 18:10