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I am running into the error message !Undefined control sequence with the below explanation and can't figure out what I'm doing wrong. I am using Mactex and Texmaker. I am new to LaTeX and would really appreciate your help!

! Undefined control sequence.
\beamer@doifinframe ...\par \begin {equation*} \x
(k) = \left ( \begin {arra...
l.123 \end{frame}
%
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., `\hobx'), type `I' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.
! Missing $ inserted.
<inserted text>
$
l.123 \end{frame}
%
I've inserted a begin-math/end-math symbol since I think
you left one out. Proceed, with fingers crossed.
! Missing } inserted

-------

The code:

   \documentclass[notes=show,beamer,t,notheorems]{beamer}

    \usepackage{amsfonts}
    \usepackage{amsmath}
    \usepackage{amssymb}
    \usepackage{mathpazo}
    \usepackage{hyperref}
    \usepackage{subfigure}
    \usepackage{tikz}

    \setcounter{MaxMatrixCols}{10}

    \newenvironment{stepenumerate}{\begin{enumerate}[<+->]}{\end{enumerate}}
    \newenvironment{stepitemize}{\begin{itemize}[<+->]}{\end{itemize} }
    \newenvironment{stepenumeratewithalert}{\begin{enumerate}[<+-| alert@+>]}{\end{enumerate}}
    \newenvironment{stepitemizewithalert}{\begin{itemize}[<+-| alert@+>]}{\end{itemize} }
    \newtheorem{assumption}{Assumption}
    \newtheorem{proposition}{Proposition}
    \usetheme{CambridgeUS}
    \setbeamertemplate{navigation symbols}{}
    \numberwithin{figure}{section}
    \setbeamertemplate{navigation symbols}{}
    \useoutertheme{umbcfootline}
    \setfootline{ \hfill \insertframenumber}
    \numberwithin{figure}{section}
    \input{tcilatex}
    \renewcommand{\QTR}[2]{\frametitle{#2}}

    \begin{document}

    \begin{equation*}
    \x(k) = \left(
        \begin{array}{c}
            x_1(k)\\
            x_2(k)\\
            \vdots\\
        \end{array} \right)

    \end{equation*}
share|improve this question
    
beamer is a presentation-style document class that requires your content to be included in a frame environment. Structural elements (like \section, say) do not have to be included in a frame, but an equation* certainly would. So use \begin{frame}...\end{frame}. –  Werner Jun 13 '13 at 20:52
3  
The error message states that \x is undefined. It's most probably a typo for x, isn't it? –  egreg Jun 13 '13 at 20:57
    
Welcome to TeX.SX! –  mafp Jun 13 '13 at 21:01

1 Answer 1

\x is udefined. You probably wanted to have x(k) = \left( instead of \x(k) = \left( just before \begin{array}.

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