LyX ⇒ Appendix theorem numbering

[CSMR]

I have some theorems in an appendix. Say Appendix A. I would like them to be numbered Lemma A1, Lemma A2,....

At the moment they are coming up as Lemma 30, Lemma 31, etc. since the numbering isn't resetting in the appendix.

I am currently using the modules Theorems(AMS) and Theorems(AMS-Extended). If I add "Theorems (Numbered by Section)" then I have the right numbering in the appendix but he wrong numbering in the main text. So I would like to switch to "Theorems (Numbered by Section)" when the appendix starts.

Any advice much appreciated.

[5gon12eder]

Would something like the following be okay for you?

Code: Select all

\documentclass{article}
\usepackage{amsthm}

\newtheorem{lemma}{Lemma}

\begin{document}
  \section{This is a document section}
  \begin{lemma}
    This is a lemma.
  \end{lemma}

  \begin{appendix}
    \section{This is an appendix section}
    \setcounter{lemma}{0}
    \renewcommand{\thelemma}{\Alph{section}\arabic{lemma}}
    \begin{lemma}
      This is another lemma.
    \end{lemma}
  \end{appendix}

\end{document}

[CSMR]

Would something like the following be okay for you?

Code: Select all

\documentclass{article}
\usepackage{amsthm}

\newtheorem{lemma}{Lemma}

\begin{document}
  \section{This is a document section}
  \begin{lemma}
    This is a lemma.
  \end{lemma}

  \begin{appendix}
    \section{This is an appendix section}
    \setcounter{lemma}{0}
    \renewcommand{\thelemma}{\Alph{section}\arabic{lemma}}
    \begin{lemma}
      This is another lemma.
    \end{lemma}
  \end{appendix}

\end{document}

Thanks for this! Yes, that works. I went in the end with defining a special environment for the appendix:
In preamble:
\newtheorem{appxlem}{Lemma}[section]
In TeX code in the appendix: \begin{appxlem} and \end{appxlem}