# How to make a box around an equation in align-environment

I would like to draw a frame around one equation to point it out. I used

\fbox{...}


but it didn't work out. Here is a minimal example where I tried it. Any package suggestions?

\documentclass[
german,
paper=a4,
]{scrbook}              %KOMA-
\usepackage[latin1]{inputenc}
\usepackage[ngerman]{babel}

\usepackage[babel,german=guillemets]{csquotes}
\usepackage[T1]{fontenc}
\usepackage{amsmath}

\begin{document}

\begin{align}
Nu_\text{m}        &= \frac{\alpha_m \, L}{\lambda}    \text{ \quad .} \\
Nu_\text{m}        &= \frac{\alpha_m \, L}{\lambda}    \text{ \quad .}
\end{align}

\end{document}

• Do you want the frame around both lines? – egreg Jul 25 '14 at 17:24
• – Werner Jul 25 '14 at 17:44

The \Aboxed command from mathtools package does what you want.

# MWE

\documentclass[
german,
paper=a4,
]{scrbook}              %KOMA-
\usepackage[latin1]{inputenc}
\usepackage[ngerman]{babel}

\usepackage[babel,german=guillemets]{csquotes}
\usepackage[T1]{fontenc}
\usepackage{amsmath,mathtools}

\begin{document}

\begin{align}
\Aboxed{Nu_\text{m}        &= \frac{\alpha_m \, L}{\lambda}    \text{ \quad .}} \\
\Aboxed{Nu_\text{m}        &= \frac{\alpha_m \, L}{\lambda}    \text{ \quad .}}
\end{align}

\end{document}