Text Formatting ⇒ Boxed and aligned Equations

[hbaromega]

I want to box multiple equations using alignment. \boxed{} environment works
fine between \begin{equation} and \end{equation}. But if we do something like the following, I find errors.

Code: Select all

\begin{align}
\boxed{
x&=y+z\nonumber\\
y&=p^2+q^2\nonumber\\
z&=2pq
}
\end{align}

Thanks.

[Stefan Kottwitz]

It works with the empheq package:

Code: Select all

\documentclass{article}
\usepackage{empheq}
\begin{document}
\begin{empheq}[box=\fbox]{align}
  x &= y+z\nonumber\\
  y &= p^2+q^2\nonumber\\
  z &= 2pq
\end{empheq}
\end{document}

Stefan

[hbaromega]

Thanks a lot, Stefan. It's working fine. I have two more questions related to this:

1) Can I set box in such a way that it includes equation numbers also?

2) Can I define a length and width for the box?

[shadgrind]

For boxing a group of aligned equations along with their labels, I use TikZ:

Code: Select all

\documentclass{article}
\usepackage{amsmath}
\usepackage{tikz}
\newcommand{\boxalign}[2][0.97\textwidth]{
 \par\noindent\tikzstyle{mybox} = [draw=black,inner sep=6pt]
 \begin{center}\begin{tikzpicture}
  \node [mybox] (box){%
   \begin{minipage}{#1}{\vspace{-5mm}#2}\end{minipage}
  };
 \end{tikzpicture}\end{center}
}
\begin{document}
\boxalign{\begin{align}
  x &= y+z\\
  y &= p^2+q^2\\
  z &= 2pq
\end{align}}

\boxalign[0.6\textwidth]{\begin{align}
  x &= y+z\\
  y &= p^2+q^2\\
  z &= 2pq
\end{align}}
\end{document}

Notice how the width of the second box was changed. There are lots of ways to customize the box with TikZ.