是否可以將單一中心方程式#應用於列表？我在第一個列表中使用用方程式對齊包裹，但 1) 它需要相當多的手動間距才能使其看起來正確，2) 長項目行為不當。項目 (iii) 被註解掉，因為它破壞了格式，我似乎無法控制它。我將不勝感激任何建議。
\documentclass[12pt, leqno]{book}
\usepackage{mathtools,amsthm}
\usepackage[shortlabels]{enumitem}
\newcommand{\blank}[1]{\hspace*{#1}}
\newcommand\abs[1]{\lvert#1\rvert}
\newcommand\dvd[2]{#1\!\mid\!#2}
\begin{document}
\noindent Using the equation env, this list is numbered and does what I want, except I'm struggling with
how to treat long lines (as in item (iii) which is commented out).
\begin{equation}
\begin{aligned}
&\text{(i) } \enspace \text{If $a>b$ then $a+c > b+c$ for every $c \in D$.} \blank{15mm} \\
&\text{(ii) } \> \text{If $a>b$ and $c>0$, then $ac>bc$.} \\
% &\text{(iii) } \text{If If $a \neq 0$ and $\dvd{d}{a}$, then $\abs{d} \leq \abs{a}$. Moreover, if $a \neq 0$, and $d \neq \pm a$, then $\abs{d} < \abs{a}$. } \\
&\text{(iv) } \text{If $a>b$ and $b>c$, then $a>c$.} \\
&\text{(v) } \> \text{If $a \neq 0$, then $a^2 > 0$.} \\
\end{aligned}
\end{equation}
\noindent Using the enumerate env handles the items perfectly with the desired formatting. I just
don't get a centered equation number.
\begin{enumerate}[labelindent=\parindent, leftmargin=*, label=(\roman*),widest=viii, align=left, noitemsep]
\item If $a>b$ then $a+c > b+c$ for every $c \in D$.
\item If $a>b$ and $c>0$, then $ac>bc$.
\item If If $a \neq 0$ and $\dvd{d}{a}$, then $\abs{d} \leq \abs{a}$. Moreover, if $a \neq 0$, and $d \neq \pm a$, then $\abs{d} < \abs{a}$.
\item If $a>b$ and $b>c$, then $a>c$.
\item If $a \neq 0$, then $a^2 > 0$.
\end{enumerate}
\end{document}
答案1
只需將枚舉環境放在\parbox.順便說一句，我認為這裡的項目編號右對齊看起來更好。我還藉此機會用 `mathtools 重新定義 \abs（因此它可以具有可變大小）：
\documentclass[12pt, leqno]{book}
\usepackage{mathtools,amsthm}
\usepackage[showframe]{geometry}
\usepackage[shortlabels]{enumitem}
\newcommand{\blank}[1]{\hspace*{#1}}
\DeclarePairedDelimiter\abs\lvert\rvert
%\newcommand\abs[1]{\lvert#1\rvert}
\newcommand\dvd[2]{#1\!\mid\!#2}
\begin{document}
\noindent Using the enumerate env handles the items perfectly with the desired formatting. I just get a centred equation number.
\begin{equation}
\parbox{0.9\linewidth}{\begin{enumerate}[labelindent=\parindent, leftmargin=*, label=(\roman*),widest=viii, labelsep=0.8em, noitemsep]
\item If $a>b$ then $a+c > b+c$ for every $c \in D$.
\item If $a>b$ and $c>0$, then $ac>bc$.
\item If If $a \neq 0$ and $\dvd{d}{a}$, then $\abs{d} \leq \abs{a}$. Moreover, if $a \neq 0$, and $d \neq \pm a$, then $\abs{d} < \abs{a}$.
\item If $a>b$ and $b>c$, then $a>c$.
\item If $a \neq 0$, then $a^2 > 0$.
\end{enumerate}}
\end{equation}
\end{document}
