Adding braces around equations

Question

Is there any way to add braces around a system of equations? Say I want to add braces around:

a=x+2y+3z

b=6x+y+2z

c=5x+3y+z

The best example I could find of how I want the braces to look is the "2d,3d,4th,5th,6th" thing here:

In other words, they need to be curly braces and appear on both sides. They also need to enclose the whole system.

Thanks!

Answer 1

Here are two possibilities, depending on what you mean by "curly".

The first type of brace grows wider the taller it gets; however, in this case, I have limited its maximum width to 3ex.

The second type of brace will never grow wider, but only taller.

EDITED to add \stackMath to perform stacks in math mode.

\documentclass{article}
\usepackage{scalerel}
\usepackage[usestackEOL]{stackengine}
\stackMath
\begin{document}
\[
\scaleleftright[3ex]{\{}
{\Centerstack{a=x+2y+3z\\
b=6x+y+2z\\
c=5x+3y+z}}
{\}}
\quad
\left\{ 
\Centerstack{a=x+2y+3z\\
b=6x+y+2z\\
c=5x+3y+z}
\right \}
\]
\end{document}

If you had a curly-brace glyph that was more to your liking from a different (importable) font, it could be used in the first method presented below.

For example, here we use the brace from the mathdesign package.

\documentclass{article}
\usepackage{scalerel}
\usepackage[usestackEOL]{stackengine}
\stackMath
\usepackage[utopia]{mathdesign}
\begin{document}
\[
\scaleleftright[3ex]{\{}
{\Centerstack{a=x+2y+3z\\
b=6x+y+2z\\
c=5x+3y+z}}
{\}}
\quad
\left\{ 
\Centerstack{a=x+2y+3z\\
b=6x+y+2z\\
c=5x+3y+z}
\right \}
\]
\end{document}

As a follow up for the OP, the mathdesign braces may be solely obtained (as \textbraceleft and \textbraceright) using the method of egreg at Import curly brackets from MathDesign (Utopia).

In the MWE below, I only import it as such. So the left hand \scaleleftright uses it, while the right-hand solution uses the default LaTeX brace. However, by uncommenting the additional code provided, these curly braces will become the default math brace.

In either case, however, the rest of the mathdesign glyphs are not imported.

\documentclass{article}
\usepackage{scalerel}
\usepackage[usestackEOL]{stackengine}
\stackMath
%\usepackage[utopia]{mathdesign}
\DeclareSymbolFont{mdsymbols}     {OMS}{mdput}{m}{n}
\DeclareSymbolFont{mdlargesymbols}{OMX}{mdput}{m}{n}
% TO GET ALL BRACES REPLACED WITH THE mathdesign BRACE
%\DeclareMathDelimiter{\lbrace}
%   {\mathopen}{mdsymbols}{"66}{mdlargesymbols}{"08}
%\DeclareMathDelimiter{\rbrace}
%   {\mathclose}{mdsymbols}{"67}{mdlargesymbols}{"09}
%
% TO JUST IMPORT mathdesign BRACES AS \textbraceleft and \textbraceright
\renewcommand{\textbraceleft}{%
  {\fontfamily{mdput}\fontencoding{OMS}\selectfont\char"66}}
\renewcommand{\textbraceright}{%
  {\fontfamily{mdput}\fontencoding{OMS}\selectfont\char"67}}
\begin{document}
\[
\scaleleftright[3ex]{$\textbraceleft$}
{\Centerstack{a=x+2y+3z\\
b=6x+y+2z\\
c=5x+3y+z}}
{$\textbraceright$}
\quad
\left\{ 
\Centerstack{a=x+2y+3z\\
b=6x+y+2z\\
c=5x+3y+z}
\right \}
\]
\end{document}

Answer 2

here's an approach that takes advantage of some matrix structures from amsmath.

the braces aren't as slinky as the ones shown in your visual, but they do stretch automatically to accommodate what's stacked inside.

i avoided the left-hand element since i didn't want to fiddle with the different levels of roots (and you didn't say that was relevant); however, in a "chain" like this, the left element is just the mirror image of what's on the right.

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\[
 \text{is the }
 \begin{Bmatrix}
  2\mathrm{d}\\3\mathrm{d}\\4\mathrm{th}\\5\mathrm{th}\\6\mathrm{th}
 \end{Bmatrix}
 \text{ root of }
 \left\{
 \begin{matrix}
  a,\\a,\\a,\\a,\\a,
 \end{matrix}
 \right.
\]
\end{document}

Answer 3

You can easily do that with the rcases environment from mathtools.

Another, cleaner solution is to use @Gonzalo Medina's code to define an lrcases environment, and its displaystyle version, dlrcases.

The following codes presents both solutions:

    \documentclass[pdf]{article}
    \usepackage{mathtools}
\usepackage{xcolor}
\usepackage{pstricks} 

    \makeatletter
    \newcases{dlrcases}{\quad}{%
      $\m@th\displaystyle{##}$\hfil}{$\m@th\displaystyle{##}$\hfil}{\lbrace}{\rbrace}
    \newcases{lrcases}{\quad}{%
      $\m@th{##}$\hfil}{{##}\hfil}{\lbrace}{\rbrace}
    \makeatother

\newcommand\oldstyleroot[2][]{%
{\let\sqrtsign\surd\sqrt[#1]{#2}}}

    \begin{document}

     \[ \oldstyleroot[3]{\frac a b}\begin{rcases}
        \sqrt a \\ \sqrt[3]a\\ \sqrt[4] a\\ \sqrt[5]a\\ \sqrt[6]a \end{rcases}
      \text{ is the }
      \begin{cases}
        \begin{rcases}
        2\mathrm{d} \\3\mathrm{d}\\4\mathrm{th}\\5\mathrm{th}\\6\mathrm{th}
        \end{rcases}
      \end{cases}
      \hskip-1em
      \text{root of }
      \begin{cases}
        a, \\a,\\a,\\a,\\a,
      \end{cases}
    \]
    \vskip 0.5cm
     \[ \begin{rcases}
        \sqrt a \\ \sqrt[3]a\\ \sqrt[4] a\\ \sqrt[5]a\\ \sqrt[6]a \end{rcases}
      \text{ is the }
      \begin{dlrcases}
        2\mathrm{d} \\3\mathrm{d}\\4\mathrm{th}\\5\mathrm{th}\\6\mathrm{th}
      \end{dlrcases}
      \text{root of }
      \begin{cases}
        a, \\a,\\a,\\a,\\a,
      \end{cases}
    \]

   \[\begin{pspicture}
 \begin{aligned}
 \sqrt a\pnode[0.25em,2ex](0,0){A}\\ \sqrt[3]a & \\ \sqrt[4] a & \\ \sqrt[5]a & \\ \sqrt[6]a \pnode[0.25em,-0.5ex](0,0){B} \end{aligned}
 \text{ is the }
 \begin{cases}
 \begin{rcases}
 2\mathrm{d} \\3\mathrm{d}\\4\mathrm{th}\\5\mathrm{th}\\6\mathrm{th}
 \end{rcases}
 \end{cases}
 \hskip-1em
 \text{root of }
 \begin{cases}
 a, \\a,\\a,\\a,\\a,
 \end{cases}
\makebox[3cm]{\psbrace(B)(A){}}
\end{pspicture}
 \]
    \end{document}