我正在根据当天的情况在一个 tex 文件中输入讲座笔记。
第一天讲座中的定理编号如下：
\newtheorem{theorem}{Theorem}
\begin{theorem}
This is Theorem number 1.
\end{theorem}
....
\begin{theorem}
This is Theorem number 20.
\end{theorem}
然后我继续用同一个文件输入第二天的讲义。但在那里，我想再次将定理编号为 1、2……而不是 21、22……
这个怎么做？
答案1
每当新的“一天”（实际上是部分）开始时，这将重置定理编号。
\documentclass{article}
\usepackage{amsmath}
\usepackage{chngcntr}
\newtheorem{theorem}{Theorem}
\counterwithin*{theorem}{section} % Remove the day number in front of the theorem number.
\begin{document}
\section{First Day}
\begin{theorem}
This is Theorem number 1.
\end{theorem}
....
\begin{theorem}
This is Theorem number 20.
\end{theorem}
\section{Another Day}
\begin{theorem}
This is Theorem number 1.
\end{theorem}
....
\begin{theorem}
This is Theorem number 20.
\end{theorem}
\end{document}