#LyX 1.3 created this file. For more info see http://www.lyx.org/ \lyxformat 221 \textclass article \language english \inputencoding auto \fontscheme default \graphics default \paperfontsize default \spacing single \papersize Default \paperpackage a4 \use_geometry 0 \use_amsmath 0 \use_natbib 0 \use_numerical_citations 0 \paperorientation portrait \secnumdepth 3 \tocdepth 3 \paragraph_separation indent \defskip medskip \quotes_language english \quotes_times 2 \papercolumns 1 \papersides 1 \paperpagestyle default \layout Title How to enter a matrix \layout List \labelwidthstring 00.00.0000 Ctrl-n Create new document \layout List \labelwidthstring 00.00.0000 Ctrl-M Insert math inset in display mode \layout List \labelwidthstring 00.00.0000 Meta-m\SpecialChar ~ [ Insert \begin_inset Formula $\left[\right]$ \end_inset \layout List \labelwidthstring 00.00.0000 Math\SpecialChar ~ panel: Insert matrix, 3 rows, 3 columns \layout Standard Now just use the cursor to navigate around the entries in the matrix. Here's how it will look: (To create the fractions, use Meta-m\SpecialChar ~ f) \layout Standard \begin_inset Formula \[ \left[\begin{array}{ccc} 1 & \frac{1}{3} & \frac{1}{2}\\ 3 & 1 & 3\\ 2 & \frac{1}{3} & 1\end{array}\right]\] \end_inset \the_end