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How do I put big brackets under different parts of an equation so that I can write, e.g., text specific to these parts?

For example:

f =  x^3 +  2
    |___|  |__| 
      |     |
   text 1  text 2
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3 Answers 3

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263

Since the text used in \underbrace (or \overbrace) is typically set in a different font size to not distract further from the equation, it is preferable to use amsmath's \text macro.

enter image description here

\documentclass{article}
% \usepackage{amsmath}
\usepackage{mathtools}% Loads amsmath
\begin{document}
\[
  f(x) = 
    \underbrace{(x + 2)^3}_\text{text 1} + 
    \bigl(
      \mathrlap{\overbrace{\phantom{(c - 2d)}}^{\text{text 2}}}
      (c - 
      \mathrlap{\underbrace{\phantom{2d) + (3e}}_{\text{text 3}}}
      2d) +
      \overbrace{(3e - 4f)}^{\text{text 4}}
    \bigr) + 
    \overbrace{(x - 3)}^\text{text 5}
\]
\end{document}

The difficult overlapping braces uses math overlaps from mathtools. It follows a process of setting the \over-/\underbrace text first with a \phantom base, after which the base (or part thereof) is re-set. However, if those aren't needed, using amsmath only would suffice for usage of \text.

There are a number of ways of achieving the overlapping output. Another method of overlapping braces is discussed in section 63.2 Overlapping braces of the mathmode document.

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  • 1
    Would you still use \text if you wanted to include math? e.g., instead of "text 1" I want to have something like $g(x)$. (Also, congrats on your 1000th answer. Awesome work!)
    – user6967
    Feb 17, 2012 at 6:12
  • @MikeWierzbicki: Thanks - 1000! No, if you use math, then you would not use \text, since math will automatically size to the appropriate font size. The switching of mode (from math to text) causes default settings to be invoked, setting text in \normalsize rather than \scriptsize. amsmath's \text chooses the appropriate text font size via \mathchoice.
    – Werner ♦
    Feb 17, 2012 at 6:28
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    Perhaps the single most useful answer on this entire forum
    – Fraïssé
    Jul 20, 2016 at 1:24
  • 1
    Good, answer, but how can I add equations since \text is used.
    – GoingMyWay
    Oct 5, 2019 at 14:38
  • 1
    @Tropilio: You can use a tabular, or array, or substack.
    – Werner ♦
    Jun 9, 2020 at 18:53
45

What you want is 

f = \underbrace{x^3}_\textrm{text 1} + \underbrace{2}_\textrm{text 2}
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  • 3
    NB syntax for overbraces, \overbrace{x^2}^\text{over}
    – innisfree
    Sep 13, 2017 at 7:57
  • 1
    For those who might be interested, with Beamer, the subcript \textrm{..} needs to be enclosed with braces: \underbrace{x^3}_ { \textrm{text 1} } otherwise it seems that there is a compilation error.
    – zetyty
    Sep 1, 2022 at 12:21
4

You would find it out in the mathmode manual or symbols manual.

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  • 4
    Please provide hyperlinks for the manuals. Not everybody may know where to find them. (I've added them for you.) Also you should consider providing more information. The poster may not know what to look for.
    – user10274
    Feb 17, 2012 at 7:53
  • 5
    The link to mathmode manual gives me a 404.
    – Reb.Cabin
    Mar 21, 2016 at 19:56

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