[Tex/LaTex] Numbering a theorem with a letter but not changing numbering of other theorems

numberingtheorems

I am wondering how to label a theorem in LaTeX using a letter but not changing the numbering of the other theorems. For example, I want Theorem 1.3 to be Theorem A and Theorem 1.4 to remain as Theorem 1.4 (not changing its numbering).

Best Answer

It's not very clear why the theorem following "Theorem A" should be numbered 1.4. So I'll give you two distinct solutions.

Solution A

\documentclass{article}
\newtheorem{thm}{Theorem}[section] % first theorem in section 1 will be 1.1
\newtheorem{thmx}{Theorem}
\renewcommand{\thethmx}{\Alph{thmx}} % "letter-numbered" theorems

\begin{document}
\begin{thm}
$0+0=0$
\end{thm}

\begin{thmx}
$0+1=1$
\end{thmx}

\begin{thm}
$1+1=2$
\end{thm}

\end{document}

The sequence will be 1.1, A, and 1.2

Solution B

\documentclass{article}
\newtheorem{thm}{Theorem}[section] % first theorem in section 1 will be 1.1
\newtheorem{thmy}{Theorem}
\renewcommand{\thethmy}{\Alph{thmy}} % "letter-numbered" theorems
\newenvironment{thmx}{\stepcounter{thm}\begin{thmy}}{\end{thmy}}

\begin{document}
\begin{thm}
$0+0=0$
\end{thm}

\begin{thmx}
$0+1=1$
\end{thmx}

\begin{thm}
$1+1=2$
\end{thm}

\end{document}

The sequence will be 1.1, A, and 1.3

Related Solutions

[Tex/LaTex] How to get the numbers for theorems, lemmas, examples, etc. before the type

Use

\swapnumbers

just before declaring your theorem-like structures. A little example:

\documentclass[11pt]{article}
\usepackage{amsthm}

\swapnumbers
\newtheorem{theo}{Theorem}[section]
\newtheorem{exam}[theo]{Example}

\begin{document}
\section{Test}
\begin{theo}
test
\end{theo}
\begin{exam}
test
\end{exam}
\end{document}

[Tex/LaTex] Theorem/Definition/Lemma problem — Numbering

Similar to the solution at this question and section 3 of the amsthm documentation:

enter image description here

\documentclass[11pt,a4paper]{report}
\usepackage{amsthm}

\theoremstyle{plain}
\newtheorem{thm}{Theorem}[chapter] % reset theorem numbering for each chapter

\theoremstyle{definition}
\newtheorem{defn}[thm]{Definition} % definition numbers are dependent on theorem numbers
\newtheorem{exmp}[thm]{Example} % same for example numbers

\newcommand{\chaptercontent}{
\section{Basics}
\begin{defn}Here is a new definition.\end{defn}
\begin{thm}Here is a new theorem.\end{thm}
\begin{thm}Here is a new theorem.\end{thm}
\begin{exmp}Here is a good example.\end{exmp}
\subsection{Some tips}
\begin{defn}Here is a new definition.\end{defn}
\section{Advanced stuff}
\begin{defn}Here is a new definition.\end{defn}
\subsection{Warnings}
\begin{defn}Here is a new definition.\end{defn}
}

\begin{document}
\tableofcontents
\part{Addition and Subtraction}
\chapter{Addition} \chaptercontent
\chapter{Subtraction} \chaptercontent
\part{Multiplication and Division}
\chapter{Multiplication} \chaptercontent
\chapter{Division} \chaptercontent
\end{document}