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I am looking for a way for counting theorems and propositions by using letters instead of numbers. Looking for on this site, I have found this code:

\newtheorem{thma}{Theorem}

\newtheorem{propa}{Proposition}

\renewcommand{\thethma}{\Alph{thma}}

\renewcommand{\thepropa}{\Alph{propa}}

However, theorems and propositions are counted separately. Is there a way for a counting like below?

Theorem A

Proposition B

Theorem C

  • 1
    Welcome to TeX-SX! As a new member, it is recommended to visit the Welcome and the Tour pages to be informed about our format and also to know about Minimal Example. Otherwise, more specifically about your question: have you tried \renewcommand{\thethm}{\Alph{thm}} ? – R. N Feb 6 at 10:11
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This will work:

\documentclass{article}
\usepackage{amsmath}
\newtheorem{thma}{Theorem}
\newtheorem{propa}[thma]{Proposition}
\renewcommand{\thethma}{\Alph{thma}}
\renewcommand{\thepropa}{\Alph{propa}}
\begin{document}
\begin{thma}
  AAA
\end{thma}
\begin{propa}
  BBB
\end{propa}
\end{document}
|improve this answer|||||
  • Thanks a lot for your help! – InsideOut Feb 6 at 9:12
  • For some reason unknown to me, I wasn't able to it 30' ago. I did it right now. – InsideOut Feb 6 at 9:43
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This should be a part of any instruduction that mentions how \newtheorem works. In this case the thma and propa envs define their own separate counters as well. But using the proper syntax you can tell propa to use the same counter as thma

\newtheorem{thma}{Theorem}
\newtheorem{propa}[thma]{Proposition}
\renewcommand{\thethma}{\Alph{thma}}

as both are not using the same counter, there is no \thepropa anymore

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  • Thanks a lot for your help! – InsideOut Feb 6 at 9:12

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