中心枚举列表（格式化数学归纳法）

Question

我正在尝试复制这个练习：

现在，我有以下内容（我将为其包含一个 MWE）。

\documentclass[11pt]{article}

\usepackage[margin=1in]{geometry}
\usepackage{amsmath,amssymb}
\usepackage{enumitem}

\newcommand{\N}{\mathbb{N}}

\begin{document}


\begin{enumerate}
    \item[2.] Prove the following variants of the Principle of Mathematical Induction:
    \begin{enumerate}
        \item For each $n\in\N$, let $P(n)$ be a proposition and let $n_0$ be some natural number. Suppose the following two results:
        \begin{enumerate}[label={(\Alph*)}]
            \item $P(n_0)$ is true.
            \item If $P(k)$ is true, then $P(k+1)$ is also true.
        \end{enumerate}
        Then $P(n)$ is true for all natural numbers $n$ such that $n\geq n_0$.
        \item For each $n\in\N$, let $P(n)$ be a proposition. Suppose the following two results:
        \begin{enumerate}[label={(\Alph*)}]
            \item $P(1)$ is true.
            \item If $P(r)$ is true for all $r$ such that $1\leq r\leq k$, then $P(k+1)$ is true.
        \end{enumerate}
        Then $P(n)$ is true for all natural numbers $n$.
    \end{enumerate}
\end{enumerate}


\end{document}

显而易见，我的复制是精确的，除了（A）-（B）列表，我不知道如何将其居中。如果我将它们封闭在环境中center，则不会发生任何事情。如果我\centering在枚举环境中添加，则两个项目都会单独居中。如果我使用varwidth通常建议的解决方案（请参阅这里），我得到的格式与我想要的不同（我猜是因为我加载了包hyperref——参见这里）。

如果您对我如何实现期望的格式有任何想法，我将非常感激，谢谢！

Answer 1

varwidthhyperref当想要设置锚点时无法开展业务。

你可以用 来模拟tabular，如果您的项目不会太长。但是，我还添加了不同的方法，只需将项目移到比enumerate应该做的更靠右的位置即可。

\documentclass[11pt]{article}

\usepackage[margin=1in]{geometry}
\usepackage{amsmath,amssymb}
\usepackage{enumitem}
\usepackage{varwidth}
\usepackage{hyperref}

\newcounter{tabitem}\newcounter{tabitemplus}
\newcommand{\tabitem}{\refstepcounter{tabitem}\makebox[\labelwidth][r]{\thetabitem\ }\ignorespaces}
\renewcommand{\theHtabitem}{\thetabitemplus\arabic{tabitem}}
\newenvironment{centerenum}[1][\Alph]
 {%
  \begin{center}
  \setcounter{tabitem}{0}\stepcounter{tabitemplus}%
  \renewcommand{\thetabitem}{(#1{tabitem})}%
  \renewcommand{\arraystretch}{1.2}
  \begin{tabular}{@{}l@{}}
 }
 {\end{tabular}\end{center}}

\newcommand{\N}{\mathbb{N}}

\begin{document}

\begin{enumerate}
% tabular
\item Prove the following variants of the Principle of Mathematical Induction:
  \begin{enumerate}
  \item For each $n\in\N$, let $P(n)$ be a proposition and let $n_0$ be some 
    natural number. Suppose the following two results:
    \begin{centerenum}
    \tabitem\label{A1} $P(n_0)$ is true.
    \\
    \tabitem\label{B1} If $P(k)$ is true, then $P(k+1)$ is also true.
    \end{centerenum}
    Then $P(n)$ is true for all natural numbers $n$ such that $n\geq n_0$.
  \item For each $n\in\N$, let $P(n)$ be a proposition. Suppose the following two results:
    \begin{centerenum}
    \tabitem\label{A2} $P(0)$ is true.
    \\
    \tabitem\label{B2} If $P(r)$ is true for all $r$ such that $0\leq r\leq k$, 
      then $P(k+1)$ is true.
    \end{centerenum}
    Then $P(n)$ is true for all natural numbers $n$.
  \end{enumerate}

% wider margin
\item Prove the following variants of the Principle of Mathematical Induction:
  \begin{enumerate}
  \item For each $n\in\N$, let $P(n)$ be a proposition and let $n_0$ be some 
    natural number. Suppose the following two results:
    \begin{enumerate}[label={(\Alph*)},leftmargin=4em]
    \item $P(n_0)$ is true.
    \item If $P(k)$ is true, then $P(k+1)$ is also true.
    \end{enumerate}
    Then $P(n)$ is true for all natural numbers $n$ such that $n\geq n_0$.
  \item For each $n\in\N$, let $P(n)$ be a proposition. Suppose the following two results:
    \begin{enumerate}[label={(\Alph*)},leftmargin=4em]
    \item $P(0)$ is true.
    \item If $P(r)$ is true for all $r$ such that $0\leq r\leq k$, then $P(k+1)$ is true.
    \end{enumerate}
    Then $P(n)$ is true for all natural numbers $n$.
  \end{enumerate}
\end{enumerate}

\end{document}

我认为，第二个例子更有吸引力。

Answer 2

您需要将其放在一个块中，然后将其作为一个单元居中。最简单的方法是使用 a，minipage但您需要指定宽度。另一种方法是varwidth使用定义可变宽度 minipage 的包。（在我看来，这会变得难以阅读，我更喜欢不居中的解决方案）。

\documentclass[11pt]{article}
\usepackage[margin=1in]{geometry}
\usepackage{amsmath,amssymb}
\usepackage{enumitem}
\newcommand{\N}{\mathbb{N}}

\usepackage{varwidth}

\begin{document}
\begin{enumerate}
\item[2.] Prove the following variants of the Principle of Mathematical Induction:
  \begin{enumerate}
  \item For each $n\in\N$, let $P(n)$ be a proposition and let $n_0$ be some natural number. Suppose the following two results:
    \begin{center}
      \begin{varwidth}{\linewidth}
        \begin{enumerate}[label={(\Alph*)},parsep=0pt]
        \item $P(n_0)$ is true.
        \item If $P(k)$ is true, then $P(k+1)$ is also true.
        \end{enumerate}    
      \end{varwidth}  
    \end{center}
    Then $P(n)$ is true for all natural numbers $n$ such that $n\geq n_0$.
  \item For each $n\in\N$, let $P(n)$ be a proposition. Suppose the following two results:
    \begin{center}
      \begin{varwidth}{\linewidth}
        \begin{enumerate}[label={(\Alph*)},parsep=0pt]
        \item $P(1)$ is true.
        \item If $P(r)$ is true for all $r$ such that $1\leq r\leq k$, then $P(k+1)$ is true.
        \end{enumerate}
      \end{varwidth}  
    \end{center}
    Then $P(n)$ is true for all natural numbers $n$.
  \end{enumerate}
\end{enumerate}
\end{document}