# Undefined control sequence \begin{document} during compiling

When I try to compile the following code in Texstudio I get error Undefined control sequence \begin{document}. I think it is related with caption. I tried everything, my texstudio is updated.

\documentclass{beamer}
\mode<presentation> {
\usefonttheme{professionalfonts}
}
\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{mathtools}
\usepackage{graphicx}
\usepackage{caption}
\usepackage[font={small,it}]{caption}
\title{Mathematics }
\subtitle{Progress report(Mini-presentation) }
\begin{document}
\section{Introduction}
\begin{columns}[T]
\column{.3\textwidth}
Stratification frequency is calculated by
$$N=\sqrt{-\frac{g}{\rho_a}\frac{d\rho_a}{dz}}$$
\column{.5\textwidth}
\includegraphics[width=0.5\linewidth]{fig11}
\captionof{figure}{Density}
\end{columns}
\section{Conclusion}
\end{document}


I need help on how to fix this error.

• Welcome to TeX.SE! Your document example (MWE: Minimal Work Example) works fine. No errors, no warnings! However, your MWE has some issues: you load caption twice, graphics is loaded by beamer, etc ... – Zarko Feb 23 '20 at 22:01
• I posted my result, Still getting the error message. Very strange! – Dereje Feb 23 '20 at 22:11
• When I take out the caption packages and the caption itself, it compiles with out error (Ofcourse with out the caption). – Dereje Feb 23 '20 at 22:17
• I overlooked, that you not use frame in your presentation. See my answer below. – Zarko Feb 23 '20 at 22:19
• note the undefined command is not \begin{document} unfortunately texstudio scrambles the error message, you need to look in the log file to see the real error message from Tex, which will show which command is undefined. – David Carlisle Feb 23 '20 at 22:40

Beamer provide own mechanism for image caption (which not work well with caption package). Its style you can define with \beamertemplate{caption}{...}, \beamerfont{caption}{...}.

I would rewrite your MWE as follows:

• used is frame environment (it is basic building block of beamer presentations)
• for image is used figure environment, but it has -- to my opinion -- sense only if you use numbered captions for images
\documentclass{beamer}
\mode<presentation> {
\usefonttheme{professionalfonts}
\setbeamertemplate{caption}[numbered]
\setbeamerfont{caption}{size=\scriptsize}
}

\usepackage{mathtools} % it also loads amsmath
\usepackage{amssymb}

\title{Mathematics }
\subtitle{Progress report(Mini-presentation) }

\begin{document}
\section{Introduction}
\begin{frame}
\begin{columns}[T]
\column{.35\textwidth}
\bigskip
Stratification frequency is calculated by
$$N=\sqrt{-\frac{g}{\rho_a}\frac{d\rho_a}{dz}}$$
\column{.45\textwidth}
\begin{figure}
\centering
\includegraphics[width=0.5\linewidth]{example-image-duck}%{fig11}
\caption{Density}
\end{figure}
\end{columns}
\end{frame}
\end{document}