# FAQ for math.stackexchange

Right now, the faq only contains the boilerplate explanations of the stackoverflow engine, reputation levels, etc.

This page serves as an index of other important support questions for the community.

Please post each faq as a separate answer, and as community wiki so we can collaboratively edit the faq. If you add a new proposed faq, add a link to it in the index.

Useful references:
The MathOverflow faq

# Index

Technical help on the user interface

Contents and tags

Other topics

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 @Willie There are two links to "Must I post in English?" (maybe this is meant as "again more slowly, please") – user53153 Jan 9 at 14:53 @PavelM: that is deliberate. See also "I used to post a lot on other math forum..." It is because I am not quite sure whether I've put the questions under the best heading. – Willie Wong♦ Jan 9 at 15:11 @Willie OK, but now that you mentioned it, the Q about everything looking different has no actual A. Why not just kill it? At the age of ever-changing UI (Facebook redesigns, etc), do people really get puzzled when one website does not look like the other? – user53153 Jan 9 at 15:42 @PavelM: -facepalm- Somehow I didn't notice that Kaestur left that one item blank when I did the reorganizing some time ago. Right, off it goes. Let me know if you see anything else. – Willie Wong♦ Jan 9 at 16:14

Q: How do I type math in my question/answer/comment?

A: For simple formulae, you can use <sup></sup> to write superscripts and <sub></sub> for subscripts:
y<sub>1</sub>=x<sup>2</sup>+3becomes y1=x2+3

For more complicated formulae, you can use TeX markup.
To type inline TeX equations, surround the code with $'s, e.g. $c = \sqrt{ a^2 + b^2 - 2ab \cos \theta }$ ⇒$c = \sqrt{ a^2 + b^2 - 2ab \cos \theta }To put the equation in its own line, surround with $$'s, e.g. $$\int_0^\infty e^{-x^2} dx = \frac{\sqrt\pi}2$$ ⇒$$\int_0^\infty e^{-x^2} dx = \frac{\sqrt\pi}2(AMS math environment is also supported, but you need 4 backslashes to produce a new line since the MarkDown engine will not be disabled in them e.g. \begin{align} \cos x &= \frac{\sin 2x}{2 \sin x} \\\\ \sin^2 x &= \cos^2 x - \cos 2x \end{align}  ⇒ \begin{align} \cos x &= \frac{\sin 2x}{2 \sin x} \\ \sin^2 x &= \cos^2 x - \cos 2x \end{align} Because of this, it is better to use ...$$ with the "-ed" environment instead. $$\begin{aligned} \cos x &= \frac{\sin 2x}{2 \sin x} \\ \sin^2 x &= \cos^2 x - \cos 2x \end{aligned}$$ ⇒$$\begin{aligned} \cos x &= \frac{\sin 2x}{2 \sin x} \\ \sin^2 x &= \cos^2 x - \cos 2x \end{aligned}$If you are unfamiliar with TeX, you can find a question that uses the markup you'd like to use, then right click and select show source. If you have detailed questions about TeX or LaTeX, this is not the appropriate place to ask them. Please use a dedicated TeX help site such as http://tex.stackexchange.com or http://www.latex-community.org/forum/ - Which famous formula? We are talking about Euler here... – Larry Wang Jul 24 '10 at 3:50 excellent addition: "If you have questions about TeX or LaTeX, this is not the appropriate place to ask them." – Tom Stephens Jul 26 '10 at 18:03 Incorporated answers from this question. – Larry Wang Aug 9 '10 at 3:03 Aside for forums for detailed TeX questions, where is a good reference on math formatting in TeX? For example, where do I find out how to format things like$\mathbb{R}$(the set of real numbers)? There is some good reference info at en.wikipedia.org/wiki/Help:Displaying_a_formula – LarsH Oct 22 '10 at 10:46 this needs to be edited to reflect the fact that $..$ blocks are not processed by markdown now. – Jeff Atwood Nov 19 '10 at 5:31 A link to the list of the$\LaTeX\$ entities supported by MathJax should be added. (I'd add it myself, but it seems to me that only mods should be editing these, and anything else is a breach.) – J. M. Dec 1 '11 at 11:43

Q: What's the relationship between math.SE and MathOverflow?

A: The purpose. MathOverflow is designed to be a website where professional mathematicians ask and answer questions that come up in their research, and consequently discourages questions that do not fit that template. Math.SE is intended for enthusiasts and users of mathematics to ask and answer questions about mathematics in general. As a result, the cultures of the two websites are very different, and they don't compete much with each other. In general, we may refer unusually difficult questions with professional interest to MathOverflow if we think you'd get a better response there.

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The relationship is the purpose? – Gerry Myerson Jun 26 '12 at 9:58

Q: What are all these dollar signs and weird symbols? It's hard to read the questions and answers with those there.

A: The things in between the dollar signs are math formulas written using the TeX markup language. On this site, such text should be automatically converted into the appropriate formatting by the MathJax script. If the strange text appears in a preview for a question/answer you are currently typing, this is normal. Wait 4 seconds, and it should automatically render.
If it is within the text of a comment that just got refreshed (typically by clicking "show more comments"), this is also normal, but hopefully will be changed in a manner consistent with previews.
If the above do not apply, and a browser refresh does not fix the problem, check whether your browser is blocking javascript (for NoScript users: note that for math formatting to work, JavaScript must be enabled not only for this site, but also for the site mathjax.org). It may also help to disable certain extensions/custom scripts if you are using Firefox.

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We need to light-up this question over at meta.stackoverflow!!!! – Tom Stephens Jul 25 '10 at 21:46
possibly related: Within the "How do I use TeX in a question?" we may want "How do I include a link in a comment?" Answer: it's just like reddit – Tom Stephens Jul 25 '10 at 21:57
Right, hopefully we'll get the site itself to use TeX rendering shortly. – Akhil Mathew Jul 25 '10 at 22:49
Old answer no longer applies. I've added info about recent changes to this site's TeX support. – Larry Wang Aug 9 '10 at 3:04

Q: What other websites should I visit to get my math questions answered?

A:

• Wolfram Alpha – for direct calculations, calculus questions, etc.

• Dr. Math – for questions from elementary to middle-undergraduate level, including calculations, more involved problems, and highly exploratory questions.

• Art of Problem Solving – AoPS is particularly good for high school and Olympiad-level contest mathematics type problems. Undergraduate mathematics is also covered in the College forum.

• StackOverflow – for programming questions. Questions about algorithms are fine on math.stackexchange. Questions about implementing algorithms should go on StackOverflow.

• Cross Validated – for questions about statistical analysis and probability theory.

• Theoretical Computer Science – StackExchange – for research level questions about theoretical computer science.

• Of course, no website is a substitute for talking to someone in person. Ask your teacher/professor/TA, they are there to help you!

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The word "trivial" here is just going to get people's backs up, even though I know what you mean. – Simon Nickerson Jul 22 '10 at 6:24
Don't forget MathOverflow for the research-level ones... – Noldorin Jul 22 '10 at 7:36
Right. Mathematicians have a reputation of abusing the word trivial; I'd say we ought to avoid that here. – Akhil Mathew Jul 22 '10 at 10:58
@Simon, @Akhil: I've replaced the word trivial, but I think it sounds awkward now. Feel free to fix it if you come up with a better phrasing. – Larry Wang Jul 22 '10 at 11:29
@Kaestur: I've changed it to the word "direct." What do you think? – Akhil Mathew Jul 22 '10 at 12:01
I haven't added MO here yet because I'm not sure how to describe it. I'm of half a mind to think that our relationship with MO deserves its own FAQ question, but I know there are people already not coming from an MO background, I think that's a good thing, and I think the MO connection will weaken in public beta and afterwards, at the very least in terms of percentage of users with MO experience. – Jamie Banks Jul 22 '10 at 17:56
I think that if a particular question is appropriate for MathOverflow, people here will notice and point it out. @Katie, @Noldorin: My impression has always been that anyone likely to have a large number of MathOverflow-type questions is probably in a university in some capacity, and so already knows of it, or has a colleague/instructor that does. Is this accurate? – Larry Wang Jul 22 '10 at 19:30
@Kaestur, I'm really not sure if that's accurate, but I think I am more skeptical that it is than you are. In particular, I went to a HS with a few outstanding math teachers who have the mathematical interest and ability, if not necessarily the training, of research mathematicians. I tended not to tell them about various authors, problems, researchers and resources that I perceived to be well-known to the mathematics community as I saw it, even if I thought they'd be interested. I've since told them more often, and frequently been surprised at what they weren't familiar with... – Jamie Banks Jul 22 '10 at 20:05
...e.g., one who loved the Feynman lectures, classical mechanics, and physical intuition used for mathematics, but didn't know of V.I. Arnold's work or books. I think there are also many high school students who may have MO-appropriate questions and not know of it (probably not in category theory, but there's a nontrivial amount of content on MO that is advanced work in accessible topics, see, e.g., much of Joseph O'Rourke's work in computational/metric geometry, or conceivably problems on things like graph theory or permutations). – Jamie Banks Jul 22 '10 at 20:09
In any case, I'm not willing to say there aren't people who would benefit from MO participation but don't know about it, and I think that's reason enough to address it. Particularly since math.SE is all about creating and exposing people to resources relating to good math questions. (sorry for the long comments). – Jamie Banks Jul 22 '10 at 20:10
@Katie: Thanks for the background. I will leave it to people more familiar with mathoverflow to decide whether this question should link there. – Larry Wang Jul 23 '10 at 0:49

Q: Why was my question closed?

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Q: What is the proper way to respond to homework questions on math.stackexchange?

A:

• Consider the guidelines given for askers of homework questions. If the question apparently lacks previous work or thought behind it, consider requesting a revision that follows these guidelines more closely.

• Give the question asker a chance to respond before voting to close.

• Providing an answer that doesn't help a student learn is not in the student's own best interest, and if a solution complete enough to be copied verbatim and handed in is given immediately, it will encourage more people to use the site as a free homework service. In the spirit of creating a lasting resource of mathematical knowledge, you may come back after a suitable amount of time and edit your response to include a more complete answer. Or even better, the student can post her or his own correct answer!

• It's much better to give a hint, so that the asker may find the right direction.

• It is encouraged to suggest other problems that use the same principles or techniques. Parallel problems are a great teaching tool.

• Don't downvote others who provide complete answers to questions just because you think it might be homework. It's not always obvious at first glance that a question is homework, especially when you're not expecting to see it. Instead, suggest editing the response in a comment.

• On the other hand, do feel free to downvote overly complete answers to known homework (as in, you know that this instance of the question is homework) if you think the asker has not done enough to 'deserve' it.

• Don't ridicule a student because they haven't yet learned something obvious.

• Be polite and encouraging! Nothing makes people hate math more than having smart people tell them they suck at it.

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I added a note saying that it's better to leave a hint, rather than spell the whole solution out. – mau Aug 2 '10 at 8:45
– Isaac Aug 2 '10 at 9:36
I added my suggestion that detailed examples should be given where possible, but to modified questions – Casebash Aug 3 '10 at 7:19
I disagree about not downvoting overdetailed answers to homeworklike questions. If the answers are edited, then it is possible to remove downvotes. This is what neo-conservatives call an existential threat to the site; the option to send a complaint stronger than a whine is important. – Charles Stewart Aug 9 '10 at 8:54
@Charles: The reason I added that is because I don't think people should be penalized for answering questions correctly and completely just because they didn't realize that someone else might (correctly or not) consider the question homework. The only thing those people did 'wrong' is to trust the person asking the question. I agree that we don't want people to provide complete answers to actual homework questions. I have edited to clarify what I mean by 'good faith.' – Larry Wang Aug 9 '10 at 18:46
@Charles: Generally commenting seems to work. I would only use downvoting if someone consistently ignores that advice – Casebash Aug 11 '10 at 12:47
@Casebash: Why is it my job to check up on whether a qner follows my advice? If I downvote, and the qner improves the question, they are very likely to ping me with an "@Charles" & I can remove the downvote. – Charles Stewart Aug 12 '10 at 12:44
This proposed piece of the FAQ has turned into something that deserves more space for discussion. – Charles Stewart Aug 12 '10 at 12:45

Q: What do I do if I don't get an answer to my question after several days?

A:

• Wait a bit longer. If it's an advanced/niche topic, the answerers may just not have seen it yet!

• Set a bounty, by sacrificing a bit of your reputation. This entices more people to have a go answering it.

• Check to make sure it is tagged properly, so the appropriate people will see your question. Overly-specific tags will mean it shows up in fewer searches. Do you really want to tag your question circles instead of geometry?

• If you think it's particularly advanced (graduate level or higher), ask if it is appropriate for Math Overflow on meta.MO.

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For your last question, I'm not sure asking on meta.MO first is the right approach. If the question is in fact graduate level, there's no reason not to go right ahead and ask it on MO. When people do ask "Is my question appropriate?" on meta.MO, this is usually because the question tests usual norms (e.g. is subjective but potentially interesting, etc.). – Akhil Mathew Jul 22 '10 at 11:15
If it is appropriate for MathOverflow, it seems there is enough overlap that people here will notice and point it out. – Larry Wang Jul 22 '10 at 11:30
@Akhil: You mean my last answer, I presume. The edit looks fine though. – Noldorin Jul 22 '10 at 12:10
The SO faq encourages updating your question with newer developments and work you've subsequently done towards a solution. That may also be appropriate here? – walkytalky Aug 12 '10 at 9:31

Q: What tags should I use for my question?

A:

• Do use, but not abuse, meta-tags such as , , , and .

• Indicate what branch of math it belongs to.

• If it is a math-related question from some other field (economics, bioinformatics, etc.), tag it with that field.

• If it is a question based on something you learned in class, tag it with the name of the class.

• Try to avoid creating new tags. Instead, check if there is some synonym that already has a popular tag.

• If you can, approximate level of the question.

• When trying to decide between two tags that fit equally well, choose the more populated one.

• If you must create a new tag: Use all lowercase, don't use symbols, and replace spaces with dashes (the useful tag number-theory with a space turns into two useless tags)

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Q: Why was my "What is [X]?" question downvoted or closed?

A:
- As you should do anytime one of your questions is downvoted or closed, see the comments people left on your question. Fix some of the issues they point out by editing your question.

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Q: Must I post in English?

A: Post in the language you are most comfortable with. Often someone will translate your question to English. Many people here would rather see a clear question that can be translated than an unclear question in English.

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Q: How do I respond to 'What is X?' questions?

A: If the question has a clear, single answer, then it is valid. For example: "What is a left coset?" is a "What is X?" question, but there is implied context.

If the question has only subjective answers, [down vote?] / [vote to close?], and request the asker to more carefully consider what they intend to learn from replies to their question - and reword the question, making it clear what they expect in reply.

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Q: Why was my question voted down?

A: It may be inappropriately phrased, try being more specific.

A: If English is not your first language, try posting in your preferred language.

A: People often downvote questions they don't understand. Try these suggestions:

• Can you include an example?
• Would it make sense to include a diagram?
• Could you explain the context of your question?
• Is there a formula that helps explain your question?
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I suspect it may be helpful to address more directly the etiquette when anyone may feel that a question and a response don't marry. I made an attempt to elaborate.

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