2

LaTeX has a command that automatically formats bracket (or parentheses, ...) to the size of what's inside them. For example :

\left\{\sum_{n\in\N}f_n(x)\right\}

Yields $\left{\sum_{n\in\N}f_n(x)\right}$. But as you can see, if you draw a line at the center of the normal line, the bottom of my example is longer than the top, and LaTeX formats depending on the maximum of the top and bottom lenghts. Thus giving a massive blanck space at the top.

Is there any way I can format the brackets myself, to make the top part of the bracket smaller ?

4
  • 1
    Welcome! Note that this site doesn't use MathJax. If you want to show the actual typeset result, include a picture.
    – egreg
    Nov 25, 2022 at 10:11
  • braces are always symmetric, and by default vertically centred. You could lower a smaller one but not usually advisable. Here as often the case, best to avoid left-right and choose a smaller { such as \bigl\{ there is no need to cover the subscript Nov 25, 2022 at 10:12
  • And thus you now know that always using \left...\right is not a good idea, learn to use the manual scalers instead: \bigl\Bigl\biggl\Biggl .. \Biggr\biggr\Bigr\bigr
    – daleif
    Nov 25, 2022 at 10:17
  • @egreg thanks, i was confused Nov 25, 2022 at 15:35

2 Answers 2

3

Here's some visual examples. Pick, among the last ones, the size you prefer.

As a general rule, \left and \right with large operators give oversized fences. The problem is exacerbated here because of the missing top limit.

Note the \, to avoid the brace colliding with the subscript.

\documentclass{article}
\usepackage{amsmath,amssymb}

\newcommand{\N}{\mathbb{N}}

\begin{document}

Here the delimiters are oversized
\[
\left\{\sum_{n\in\N}f_n(x)\right\}
\]

This is even worse
\[
\left\{\sum_{\substack{n\in\N \\ n>0 }}f_n(x)\right\}
\]

But this is much better
\[
\Bigl\{\,\sum_{n\in\N}f_n(x)\Bigr\}
\]

Even with a two-line subscript
\[
\Bigl\{\,\sum_{\substack{n\in\N \\ n>0 }}f_n(x)\Bigr\}
\]

You may want \verb|\bigg|, but I wouldn't
\[
\biggl\{\,\sum_{n\in\N}f_n(x)\biggr\}
\qquad
\biggl\{\,\sum_{\substack{n\in\N \\ n>0 }}f_n(x)\biggr\}
\]

\end{document}

enter image description here

1
  • Thanks for your solution. I was just wondering if there were any packages for that, but I guess not then Nov 25, 2022 at 15:36
1

You do not need to extend over the subscript here.

enter image description here

\documentclass{article}

\usepackage{amsmath,amsfonts}
\newcommand\N{\mathbb{N}}%grumble, definition not supplied
\begin{document}

\centering

left
\[\left\{\sum_{n\in\N}f_n(x)\right\}\]


Big
\[\Bigl\{\sum_{n\in\N}f_n(x)\Bigr\}\]

\end{document}

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