（1）这是标记和引用非定理环境的正确方法吗？
（2）我们能否将句子写成“案例 2.1.1、2.1.2、2.1.3”，即将其添加到定理编号中？
（3）或者，我们是否可以通过手动输入将其定制为“案例 2.1.1、2.1.2、2.1.3”（或任何所需的编号）？
\usepackage{textcomp}
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\usepackage{mathtools}
\usepackage{amsmath}
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\usepackage[a4paper,left=1in,top=1in,right=1in,bottom=1in,nohead]{geometry} %margin of 1 inch
\usepackage[hidelinks]{hyperref}% for hyperlinks
\titleformat{\section}[block]{\large\scshape\bfseries}{\thesection.}{1em}{} % Change the look of the section titles
\titleformat{\subsection}[block]{\bfseries}{\thesubsection.}{1em}{} % Change the look of the section titles
\newtheorem{thm}{Theorem}[section]
\newtheorem{ppn}[thm]{Proposition}
\newtheorem{cor}[thm]{Corollary}
\newtheorem{lem}[thm]{Lemma}
\newtheorem{con}[thm]{Conjecture}
\begin{document}
\section{FiRsT section}
\section{SeCoNd section}
In this section, we shall prove Theorem \ref{thm1}. In the proof, we split into Cases \ref{case2.1.1}, \ref{case2.1.2}, and \ref{case2.1.3}. %Can we make the sentence appear as "Cases 2.1.1, 2.1.2, 2.1.3", i.e., it adds on to the theorem numbering? Alternatively, is there a way we can customise it to "Cases 2.1.1, 2.1.2, 2.1.3"(or any desired numbering) by inputting manually?
\begin{thm}
For any integers $m,n$, $\max\{m,n\}+\min\{m,n\}=m+n$
\\\noindent\textit{Proof}:
\\Case 1. $m< n$. \label{case2.1.1}
\noindent\par Then, $\ldots$
\\
\\Case 2. $m>n$.\label{case2.1.2}
\noindent\par Then, $\ldots$
\\
\\Case 3. $m=n$.\label{case2.1.3}
\noindent\par Then, $\ldots$
\end{thm}
\end{document}
