下面的例子：
\documentclass{standalone}
\begin{document}
% outer minipages are not part of the test, and just demonstrate the inconsistency
\begin{minipage}[t]{0.5\textwidth}
This is an equation
\begin{equation}
x = 1,
\end{equation}
which ends in a comma.
\end{minipage}%
\begin{minipage}[t]{0.5\textwidth}
This is a minipage equation\par
\begin{minipage}[t]{\textwidth}
\begin{equation}
x = 1,
\end{equation}
\par\nointerlineskip\xdef\tpd{\the\prevdepth}
\end{minipage}%
\par\prevdepth\tpd\noindent
which ends in a comma.
\end{minipage}%
\end{document}
prevdepth东西是从哪里拿走的https://tex.stackexchange.com/a/34982/41112，呈现为
如何才能使右侧的列与左侧的列匹配，而无需删除小页面？请注意，$x=1$ 行也未对齐，尽管只是轻微的。
编辑：事实证明这是一个 XY 问题，而我上述问题的解决方案实际上并不适用于实际问题。即：
\documentclass{article}
\usepackage{amsmath}
\usepackage{xcolor}
\begin{document}
This is some text that is long enough to wrap across multiple lines, or at least it ought to be. This gap is too big:\par\nointerlineskip\noindent
\begin{minipage}[t]{.5\textwidth}%
\begin{subequations}\label{eq:tensor_tensor_tensor_left}%
\begin{alignat}{2}%
&
(M \otimes_{\color{red} R} N) \otimes_{\color{blue} A} (P \otimes_{\color{red} R} Q) \nonumber \\
\cong_{\color{blue} A} {}&
((M \otimes_{\color{red} R} N) \otimes_{\color{blue} A} P) \otimes_{\color{red} R} Q) \label{eq:ttt-left-assoc-1}
\end{alignat}%
\end{subequations}%
\end{minipage}%
\begin{minipage}[t]{.5\textwidth}%
\begin{subequations}\label{eq:tensor_tensor_tensor_right}%
\begin{alignat}{2}%
&
(M \otimes_{\color{red} R} N) \otimes_{\color{blue} A} (P \otimes_{\color{red} R} Q) \nonumber \\
\cong_{\color{blue} A} {}&
M \otimes_{\color{red} R} (N \otimes_{\color{blue} A} (P \otimes_{\color{red} R} Q) \label{eq:ttt-right-assoc-1}
\end{alignat}%
\end{subequations}%
\par\xdef\tpd{\the\prevdepth}%
\vspace*{\belowdisplayskip}\vspace*{-\baselineskip}%
\end{minipage}\par\prevdepth=\tpd\noindent
and some more unindented text. The gap above is too small. Toegther they add to the right amount.
\begin{alignat}{2}%
&
(M \otimes_{\color{red} R} N) \otimes_{\color{blue} A} (P \otimes_{\color{red} R} Q) \nonumber \\
\cong_{\color{blue} A} {}&
M \otimes_{\color{red} R} (N \otimes_{\color{blue} A} (P \otimes_{\color{red} R} Q) \label{eq:ttt-right-assoc-1}
\end{alignat}%
These two gaps are just right, and is a bit bigger than the one above
\end{document}
这使：
答案1
让我修改一下您的示例，这样第二个外部小页面只是为了与第一个小页面并排显示效果。在第二个小页面中，第一行和公式在小页面中，后面的文本在外面。
\documentclass{article}
\begin{document}
% outer minipages are not part of the test, and just demonstrate the inconsistency
\noindent
\begin{minipage}[t]{0.5\textwidth}
This is an equation
\begin{equation}
x = 1,
\end{equation}
which ends in a comma.
\end{minipage}%
\begin{minipage}[t]{0.5\textwidth}
\begin{minipage}[t]{\linewidth}
This is a minipage equation
\begin{equation}
x = 1,
\end{equation}
\par\xdef\tpd{\the\prevdepth}%
\vspace*{\belowdisplayskip}\vspace*{-\baselineskip}
\end{minipage}\par\prevdepth=\tpd
which ends in a comma.
\end{minipage}
\end{document}
然而，这可能在很多方面失败，因为等式后面的跳过可能是\belowdisplayshortskip，并且需要一个相当复杂的程序来确定它。
有关真实的问题，我建议按照以下思路来处理https://tex.stackexchange.com/a/550010/4427
较\mathcolor{red}{R}喜欢\color{red} R。
\documentclass{article}
\usepackage{amsmath}
\usepackage{xcolor}
\newcommand{\sidebysidesubequations}[5][0.5]{%
$$% Yes! We're consciously doing it
\begin{minipage}{#1\displaywidth}%
\setlength{\abovedisplayskip}{0pt}%
\begin{subequations}\label{#2}
\noindent#3
\end{subequations}
\end{minipage}
\begin{minipage}{\dimeval{\displaywidth-#1\displaywidth}}
\setlength{\abovedisplayskip}{0pt}%
\begin{subequations}\label{#4}
\noindent#5
\end{subequations}
\end{minipage}
$$%
}
\begin{document}
This is some text that is long enough to wrap across multiple lines, or
at least it ought to be.
\sidebysidesubequations{eq:tensor_tensor_tensor_left}{
\begin{align}
& (M \otimes_{\mathcolor{red}{R}} N)
\otimes_{\mathcolor{blue}{A}}
(P \otimes_{\mathcolor{red}{R}} Q) \nonumber \\
\cong_{\mathcolor{blue}{A}} {}&
M \otimes_{\mathcolor{red}{R}}
(N \otimes_{\mathcolor{blue}{A}} (P \otimes_{\mathcolor{red}{R}} Q) \label{eq:ttt-left-assoc-1}
\\
& (M \otimes_{\mathcolor{red}{R}} N)
\otimes_{\mathcolor{blue}{A}}
(P \otimes_{\mathcolor{red}{R}} Q) \nonumber \\
\cong_{\mathcolor{blue}{A}} {}&
M \otimes_{\mathcolor{red}{R}}
(N \otimes_{\mathcolor{blue}{A}} (P \otimes_{\mathcolor{red}{R}} Q) \label{foo1}
\end{align}
}{eq:tensor_tensor_tensor_right}{
\begin{align}
& (M \otimes_{\mathcolor{red}{R}} N)
\otimes_{\mathcolor{blue}{A}} (P \otimes_{\mathcolor{red}{R}} Q) \nonumber \\
\cong_{\mathcolor{blue}{A}} {}&
M \otimes_{\mathcolor{red}{R}}
(N \otimes_{\mathcolor{blue}{A}} (P \otimes_{\mathcolor{red}{R}} Q) \label{eq:ttt-right-assoc-1}
\\
& (M \otimes_{\mathcolor{red}{R}} N)
\otimes_{\mathcolor{blue}{A}} (P \otimes_{\mathcolor{red}{R}} Q) \nonumber \\
\cong_{\mathcolor{blue}{A}} {}&
M \otimes_{\mathcolor{red}{R}}
(N \otimes_{\mathcolor{blue}{A}} (P \otimes_{\mathcolor{red}{R}} Q) \label{foo2}
\end{align}
}
and some more unindented text
and some more unindented text
and some more unindented text
and some more unindented text.
\begin{align}
& (M \otimes_{\mathcolor{red}{R}} N)
\otimes_{\mathcolor{blue}{A}} (P \otimes_{\mathcolor{red}{R}} Q) \nonumber \\
\cong_{\mathcolor{blue}{A}} {}&
M \otimes_{\mathcolor{red}{R}}
(N \otimes_{\mathcolor{blue}{A}}
(P \otimes_{\mathcolor{red}{R}} Q) \label{eq:ttt-right-assoc-2}
\end{align}
These two gaps are just right, and is a bit bigger than the one above
\end{document}
