When to use \dots, \ldots, \cdots, and blanks?

Question

I am writing math. questions like these:

Complete the missing numbers: 3,4,...,...,7
5+...=7
The rectangle contains four ... angles (choices: acute, obtuse or right)

In each case of the mentioned ones, which is the suitable to use? (dots - ldots - cdots - a blank)

\dots is an amsmath macro that tries to automate the choice between ldots and cdots (by looking at the following symbol mostly) — David Carlisle, Oct 22 '15 at 18:23
relevant, though not duplicates: \dots versus \ldots - is there a difference? and Difference of the \dots* — barbara beeton, Oct 22 '15 at 18:25
@barbarabeeton: The first asks "when to use \dots and/or \ldots"... for me a clear duplicate. — Werner, Oct 22 '15 at 18:26
@werner -- to some extent i agree, but it doesn't cover \cdots, which is why i referred to the second question as well. — barbara beeton, Oct 22 '15 at 18:33
The referred questions are neglecting the issue of when to use it specifically. So, i need more clarification and i put these examples to get your help. — Ayman Osama, Oct 22 '15 at 18:49
@AymanOsama: Note that such a question (in general) could be considered opinion-based. Where I like the look of \cdots, others may feel \ldots are sufficient. — Werner, Oct 22 '15 at 19:28
I don't think this is a duplicate. The topic of this question isn't really when to use which \*dot*, but rather how to typeset the kind of exercises that OP showed. Only the title is very misleading. — Wauzl, Oct 22 '15 at 21:27
Please suggest a new title and i can change it. I hope also to find a clear answer to the question. — Ayman Osama, Oct 23 '15 at 06:12
@Werner I don't think it's an opinion-based question. I am sure there is a rule to differentiate between dots between numbers in a series and numbers between operators, and other types of dots. — Ayman Osama, Oct 23 '15 at 06:14

score 4 · Accepted Answer · answered Oct 22 '15 at 19:07

AMS offers several dot (ellipsis) styles, use the one matching your intent:

\dotsc: For use between commas, e.g a, b, \dotsc, z
\dotsb: To elide binary operators, like a_n z^n + a_{n - 1} z^{n - 1} + \dotsb + a_0
\dotsm: Ditto, multiplications, as in n! = n \cdot (n - 1) \dotsm 1

There is also a set for use in arrays (matrices).

In general, I've found that the extra work to select the precise alternative instead of hoping LaTeX will Always Do The Right Thing is minimal, and pays off in better results (as said LaTeX selection is based on very limited information).

score 4 · Answer 2 · answered Oct 22 '15 at 19:16

Since what you try to do is like a cloze text, consider using underlines. This is (from what I recall) what a cloze text should have.

You could do it like this

The rectangle contains \underline{\;\phantom{right}\;} angles.

producing

This will work in maths environment, as well. I added \; for some extra spacing.

When to use \dots, \ldots, \cdots, and blanks?

2 Answers2

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