What is the difference between \big[
(or equivalently \big(
) and \bigl[
? Is it always necessary to mention l
(left) and r
(right)?
2 Answers
\bigl
declares an opening math delimiter with less horizontal spacing than the unspecified \big
. \bigr
defines a closing math delimiter. Using a \bigl
and \bigr
pair you could get the brackets or parentheses closer to the term within.
Just compare:
\documentclass{article}
\begin{document}
$\bigl[ \times \bigr]$
$\big[ \times \big]$
\end{document}
Output:
The definitions in latex.ltx are:
\def\bigl{\mathopen\big}
\def\bigm{\mathrel\big}
\def\bigr{\mathclose\big}
-
3Is there a way to make this distinction without specifying a larger size? Aug 6, 2010 at 17:30
-
10For normal brackets it's automatically done. Compare
$[ \times ]$
to$\mathord[ \times \mathord]$
.– Stefan Kottwitz ♦Aug 6, 2010 at 17:48 -
5What you're saying is that
[
is automatically interpreted as an opening math delimiter, so one must manually force it not to be, if desired; is that right? Aug 6, 2010 at 19:18 -
6That's true. fontmath.ltx defines:
\DeclareMathDelimiter{[}{\mathopen} {operators}{"5B}{largesymbols}{"02}
– Stefan Kottwitz ♦Aug 6, 2010 at 19:45 -
1
You can see the difference in the following example. The left modifiers \bigl
etc. are basically \mathopen{}\big
. You also have to use \mathopen
if you are using \left
and \right
to do automatic scaling to get correct spacing in some cases.
\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{align}
x &= \sin\biggl(\frac12\biggr) \\ % good
x &= \sin\mathopen{}\bigg(\frac12\bigg) \\ % good
x &= \sin\bigg(\frac12\bigg) \\ % bad
x &= \sin\left(\frac12\right) \\ % bad
x &= \sin\mathopen{}\left(\frac12\right) % good
\end{align}
\end{document}
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1I see. So what I now understand is that one should use
\mathopen{}
for a function, e.g.,f\mathopen{}\left(x^{2^2}\right)
, but don’t use it for a multiplication, e.g.,x \cdot \left(x^{2^2}\right) = x \left(x^{2^2}\right)
. It would be great if someone with some typographic experience could confirm! (Alternatively, I could open a new question.) Mar 13, 2018 at 20:26 -
It's not 100% clean when one should use either. Is
\mathopen{}
only for function arguments?– mu7zJun 17, 2020 at 22:33
$]x[$
vs.$\left]x\right[$
or any of the\big
versions.