# Extend box around equation to the entire line

My question is simple: I use \boxed from the amsmath package and so far so good.

The single issue I have is that I use the boxed environment on its own line, but the box is only around the equation, not the entire line.

Example code:

  $\boxed{ p(v,h) = \frac{1}{Z} e ^{-E(v,h)} }$


How can I extend the box to the entire line?

Thank you!

## 2 Answers

Use the environment mdframed instead of the command \boxed

MWE:

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

\begin{document}

\begin{mdframed}
$p(v,h) = \frac{1}{Z} e ^{-E(v,h)}$
\end{mdframed}

\end{document}


Output:

If you need any background you can add a backgroundcolor option to the mdframed environment.

For example:

\documentclass{article}
\usepackage{amsmath,mdframed,xcolor}

\begin{document}

\begin{mdframed}[backgroundcolor=green!10]
$p(v,h) = \frac{1}{Z} e ^{-E(v,h)}$
\end{mdframed}

\begin{mdframed}[backgroundcolor=cyan!20]
$$p(v,h) = \frac{1}{Z} e ^{-E(v,h)}$$
\end{mdframed}

\end{document}


Output:

My solution is a little more unusual, but in the end it lets you keep the equation numbering and lets you highlight the box containing the equation.

To achieve that I defined a \newcommand which I called \fancyboxed which has the following synopsis:

\fancyboxed[<background color>]{<equation>}

Please note that in this case the argument <equation> is already in math mode, so you don't have to insert things such as $...$, $...$, etc.

The basic idea behind my solution was to treat the equation as the argument of a (rectangular) tikz node spanning the entire \linewidth.

Here is the code:

\documentclass{article}
\usepackage{tikz}          %drawing
\usepackage{amsmath}
\usepackage{lipsum}        %dummy text
\newcommand{\fancyboxed}[2][white]{      %white is default background
$$\tikz \node at(0,0) [shape=rectangle,draw,thick,minimum width=\linewidth,fill=#1] {\displaystyle #2};$$
}
\begin{document}
\lipsum[1]
\fancyboxed{p(v,h) = \frac{1}{Z} e ^{-E(v,h)}}
\fancyboxed[red!30]{p(v,h) = \frac{1}{Z} e ^{-E(v,h)}}
\lipsum[2]
\end{document}