How do I refer to labels in a document from a beamer presentation?

Question

I have a thesis class document with about 200 definitions, theorems and lemmas along with a beamer presentation. While I’m presenting, my audience will be referring to the document. How can I have beamer use the same numbering as the document in my presentation?

If I do nothing, beamer assigns new numbers to all of the definitions, theorems, and lemmas, which will be confusing. And because there’s so many items, manually numbering them isn’t an option.

Answer 1

You could directly refer to the number of the theorem in your thesis using the xr package.

Let's say your thesis looks like this:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}

\newtheorem{theorem}{Theorem}

\begin{document}
\section{Introduction}
Theorems can easily be defined

\begin{theorem}
Let $f$ be a function whose derivative exists in every point, then $f$ 
is a continuous function.
\end{theorem}

\begin{theorem}
\label{mytheo}
Let $f$ be a function whose derivative exists in every point, then $f$ 
is a continuous function.
\end{theorem}

Refering: \ref{mytheo}
\end{document}

Then you can use the labels with in your presentation:

\documentclass{beamer}

\usepackage{xr}
\externaldocument{document2}

\setbeamertemplate{theorems}[numbered]
\usepackage{refcount}


\begin{document}
\begin{frame} 
test \ref{mytheo}


\setcounterref{theorem}{mytheo}
\addtocounter{theorem}{-1}
\begin{theorem}
Let $f$ be a function whose derivative exists in every point, then $f$ 
is a continuous function.
\end{theorem}

\end{frame}
\end{document}