How can I stop equations from moving up into blank space?

Question

My document has a number of equations that are surrounded by text. After long sentences, the equations look fine. However, after short sentences, they do not: the problem is that the equations are 'shifting up' into the empty space.

Is there a solution to this? One option is to add lots of white text above equations (to lengthen short sentences) but I imagine that better solutions are available.

Here is an example (I wasn't sure what might be relevant so have erred on the side of inclusion):

\documentclass[12pt,a4paper]{article}

\begin{document}

**Example 1 (no problem)**. This is a 'long sentence' followed by
\begin{equation} 2x = 10 \end{equation}

**Example 2 (problem)**
\begin{equation} 2x = 10 \end{equation}

\end{document}

Could you please post a small compilable code illustrating your problem? — Bernard, Dec 19 '19 at 16:16
Welcome to TeX SE. Could you add a minimal working example reporducing the behavior? — Alain Remillard, Dec 19 '19 at 16:17
First see what happens if you delete the blank lines between text and equation. Second: if you compile with latex , don't use the plain TeX construct $$ ... $$, use \[ ... \] instead. — Bernard, Dec 19 '19 at 16:34
Many thanks for the suggestions. However, the issue persists if I use [ ] (or delete the blank space). Perhaps this kind of spacing is just a standard feature of Latex? — afreelunch, Dec 19 '19 at 16:37
Instead of giving some "potentially relevant information" please provide a full minimal working example which starts with \documentclass{...} and ends with \end{document}. Maybe you want to give \abovedisplayshortskip the same value as \abovedisplayskip but maybe there is something else going on (e.g. blank lines as Bernard pointed out). — campa, Dec 19 '19 at 16:37
See also Why is \[ ... \] preferable to $$ ... $$? and What are the differences between $$, \[, align, equation and displaymath? — Mico, Dec 19 '19 at 16:38
I have added some more information, hopefully it is helpful? — afreelunch, Dec 19 '19 at 16:52
I added an image of the output from your test file but the output is the opposite to your description, the first example has a short line above the display (so uses the small vertical space) the second example has less text but a longer line above the display so uses the larger vertical space — David Carlisle, Dec 19 '19 at 18:23
Hi @DavidCarlisle thanks for doing this, yes there is no problem at all when you do it! This is rather odd... — afreelunch, Dec 19 '19 at 18:25
@afreelunch yes there is exactly the same problem but the short skip is used on the first example and the normal skip is used on the second. If you make these equal as I suggest in my answer, you will get equal spacing by some definition but the space in the first example will look very large as by eye you see the space to the tex above the equation not to the space to the line with only half a word. So my answer gives what you asked for, but be careful of what you ask.... — David Carlisle, Dec 19 '19 at 18:29

David Carlisle · Answer 1 · 2019-12-19T18:37:15.897

3

If the last line of the paragraph is short more than 2em to the left of the equation then Tex uses a different spacing, if you do not like this you can set the space for this case to be same as the overlapping case:

\setlength\abovedisplayshortskip{\abovedisplayskip}
\setlength\belowdisplayshortskip{\belowdisplayskip}

edited Dec 19 '19 at 18:37

answered Dec 19 '19 at 18:26

David Carlisle

757,742

Thanks so much! Can I ask where I put these commands? I tried putting them in the document I received an error message (specifically, 'missing number, treated as zero') – afreelunch Dec 19 '19 at 18:32
@afreelunch anywhere before the equation but I had a typo with ( instead of { so you need the fixed version as above (now:-) – David Carlisle Dec 19 '19 at 18:37
Uhm, actually the best way should be to patch \normalsize, wouldn't it? – campa Dec 20 '19 at 09:25
@campa possibly although most documents shouldn't have global size changes mid document so a single setting should be fine (and patching normalsize is a bit tricky as you also have to take account of \@normalsize and for newer formats \normalsize<space> which would mean that 90% of the answer was about how to patch normalsize and not about display math spacing. – David Carlisle Dec 20 '19 at 09:34

How can I stop equations from moving up into blank space?

1 Answers1