Uwe St�hr wrote:
see attached example.
Sorry, I attached a wrong file. Now the correct one.
regards Uwe
#LyX 1.3 created this file. For more info see http://www.lyx.org/
\lyxformat 221
\textclass article
\begin_preamble
\newcommand{\ketmatrix}[1]{\left|#1\right>}
\end_preamble
\language english
\inputencoding auto
\fontscheme default
\graphics default
\paperfontsize default
\spacing single
\papersize Default
\paperpackage a4
\use_geometry 0
\use_amsmath 1
\use_natbib 0
\use_numerical_citations 0
\paperorientation portrait
\secnumdepth 3
\tocdepth 3
\paragraph_separation skip
\defskip medskip
\quotes_language english
\quotes_times 2
\papercolumns 1
\papersides 1
\paperpagestyle default
\bullet 1
1
34
-1
\end_bullet
\bullet 2
2
35
-1
\end_bullet
\bullet 3
2
7
-1
\end_bullet
\layout Standard
\begin_inset Formula \[
\ketmatrix{\begin{matrix}a & b\\
c & d\end{matrix}}\]
\end_inset
\the_end
