# Redefining a theorem counter

I have a document with a lot of lemmas and theorems. In the main part of the document there are sections and subsections, so I defined

\newtheorem{lem}{Lemma}[subsection]


to number the lemmas accordingly. But in the appendices I don't have subsections, so I figured it would be better if lemmas in the appendices are not numbered with respect to subsections, but with respect to sections. Therefore, I gave the command

\renewcommand\thelem{\thesection.\arabic{lem}}


just after opening the appendices with \appendix. But something strange happened. In appendix A I don't have lemmas. In appendix B the first lemma is numbered B.3. Could anyone explain me this behavior and suggest a solution?

Edit: If I give the command

\renewcommand\thelem{\thesection.\arabic{lem}}
\setcounter{lem}{0}


the first lemma will be numbered B.1. But I'm still confused about why it is necessary to set the counter to 0.

-

\makeatletter

Ah sorry, I commented away \renewcommand\thelem... (which is silly, I admit). It works now, thanks! –  Egbert May 31 '12 at 12:28