# Reduce large parenthesis or brackets

I am using \left[ and \right] around a mathematical formula that has also an \underbrace.

$$\sum\limits_{i=1}^{Nc}{\left[\frac{\partial \dot{m}_{i}}{\partial z}\hat{h}_{i} + \dot{m}_{i}\underbrace{\frac{\partial \hat{h}_{i}}{\partial T}}_{c_{p i}}\frac{\partial T}{\partial z} \right]}dz$$


The brackets include also the underbrace and its text, which I do not want.

How do I get them to be smaller?

I am using

\usepackage{amsfonts}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{graphicx}
\usepackage{indentfirst}
\usepackage{url}
\usepackage{color}
\usepackage{cancel}
\usepackage{float}
\numberwithin{equation}{section}

• Use \biggl[ and \biggr] instead of \left[ and \right]. By the way, there's no need of \limits nor of bracing the formula after \sum: \sum_{i=1}^{Nc} \biggl[... is correct and simpler. – egreg Jan 6 '15 at 10:36

## 1 Answer

As @egreg suggests, you can force the size of the delimiters. I'll also suggest to use \underbracket (from mathtools) rather than \underbrace here: in my opinion, for small parts of formulae, \underbrace doesn't look too nice. With \underbracket, you can adjust line thickness and bracket height:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{mathtools}

\numberwithin{equation}{section}

\begin{document}
\setcounter{section}{3}
$$\sum\limits_{i=1}^{Nc}{\biggl[\frac{\partial \dot{m}_{i}}{\partial z}\hat{h}_{i} + \dot{m}_{i}\underbracket[0.4pt][2pt]{\frac{\partial \hat{h}_{i}}{\partial T}}_{c_{p i}}\frac{\partial T}{\partial z} \biggr]}dz$$

\end{document}


• That is perfect, thank you! I have to install the mathtools package to use \underbrackets, but I actually like \underbrace, and I used it in other equations too. I'll see with my professors what they think. – laureapresa Jan 6 '15 at 12:18
• In your documents, you can replace loading amsmath with loading mathtools, since the latter loads amsmath. It has many useful possibilities. – Bernard Jan 6 '15 at 12:21