# Can we ask question by referring the equations, say, in an article in Wikipedia?

I was reading about "Poisson summation formula" in Wikipedia, yet there is something I can't understand. So can I copy the link and say I did not understand this and this in that link?

It seems wrong because I don't remember seeing such questions but if it is ok, easier.

## 2 Answers

If it is at all possible you should make the question self-contained, that is you should reproduce the relevant content here (mentioning the source, and linking it for further context).

There may be cases where this is not possible, but often they will result in too broad or otherwise unsuitable questions.

• This is especially relevant for a source like Wikipedia, where the text is likely to change and so the question may not make sense to readers coming back months later. – Eric Wofsey Dec 23 '15 at 23:24

This is closer to a comment than to an answer, but I will point out few details:

• It is good to mention the source of your question. (In this case, a Wikipedia article.) But since the Wikipedia articles change, it might be a good idea to add also link to the current revision. (If you click on "View History", you can see list of revisions. From there, you can also obtain a link to a particular revision, like this one.)
• Usually,1 it should be relatively easy to copy a formula from Wikipedia. This might browser-dependent, but probably already selecting the formula and trying to copy-paste will give you a format suitable to use here. But what should work reliably is viewing the source (by clicking on edit), finding the formula there and copying it. For example, in the article you mentioned you can find this: \sum_{n=-\infty}^\infty f(n)=\sum_{k=-\infty}^\infty \hat f\left(k\right). Exactly the same syntax works here: $$\sum_{n=-\infty}^\infty f(n)=\sum_{k=-\infty}^\infty \hat f\left(k\right).$$

1For simple and inline formulas, you will often find some combination of HTML and Wikipedia syntax, like here: L<sup>1</sup>('''R'''). So this only works for formulas enclosed in $...$.