☰

如何在 align* 内框住两行

tag-icon • tag-icon math-mode boxes align
如何在 align* 内框住两行

我问了一个类似问题今天，除了它针对的是align*环境中的某一行之外。现在我想封闭两行。下面的失败尝试清楚地表明了我的意图：

\begin{align*}
\ce{K_a $\times$ K_b} &= \ce{K_w}\\
-\log(\ce{K_a $\times$ K_b}) &= -\log\ce{K_w}\\
 -( \log(\ce{K_a}) + \log(\ce{K_b}) ) &= -\log\ce{K_w} & \text{(Using log law for LHS.)} \\
 - \log(\ce{K_a}) - \log(\ce{K_b}) &= -\log\ce{K_w}\\
\fbox{
 \begin{minipage}{\textwidth}
\ce{pK_a} + \ce{pK_b} &= \ce{pK_w}\\
&=14.00 \text{ (at \SI{25}{\celsius})}\\
\end{minpage}
}
\end{align*}

\Aboxed来自mathtoolspkg 是一个很好的解决方案，您不必指定强制参数，而且它很简单Aboxed{ }- 可惜它只适用于单行框。

至于\Aboxed我不想被问到盒子应该有多宽——它应该自动确定。

和往常一样，我更喜欢预定义的解决方案，以及较少干扰的代码来实现所需的效果。越少混乱越好。

顺便说一下，本手册似乎表明\mbox，类似地\fbox应该在封闭的内容周围绘制框架。以前我无法\mbox显示可见的框架...

答案1

这里有一个灵感tikz

（欢迎大家修改示例--我不熟悉tikz）

\documentclass{article}
\usepackage{mathtools}
\usepackage{mhchem}
\usepackage{siunitx}

\usepackage{tikz}
\newcounter{markeq}
\setcounter{markeq}{0}
\newcommand*\bmarkeq{%
   \stepcounter{markeq}%
   \tikz[remember picture]\node(startframe-\themarkeq){\strut};}
\newcommand*\emarkeq{%
   \begin{tikzpicture}[remember picture,overlay]
     \node (endframe-\themarkeq){\strut};
     \draw[,red,opacity=0.8] (startframe-\themarkeq.north) rectangle (endframe-\themarkeq.south);
   \end{tikzpicture}%
}

\begin{document}


\begin{align*}
\ce{K_a $\times$ K_b} &= \ce{K_w}\\
-\log(\ce{K_a $\times$ K_b}) &= -\log\ce{K_w}\\
 -( \log(\ce{K_a}) + \log(\ce{K_b}) ) &= -\log\ce{K_w} & \text{(Using log law for LHS.)} \\
 - \log(\ce{K_a}) - \log(\ce{K_b}) &= -\log\ce{K_w}\\
\bmarkeq\ce{pK_a} + \ce{pK_b} &= \ce{pK_w}\\
&=14.00 \text{ (at \SI{25}{\celsius})}\emarkeq
\end{align*}


\end{document}

编辑

借助 egreg 的伟大创意，您可以获得：

\documentclass{article}
\usepackage{mathtools}
\usepackage{mhchem}
\usepackage{siunitx}

\usepackage{tikz}
\newcounter{markeq}
\setcounter{markeq}{0}

\newcommand{\pstrut}[1]{\vrule height0pt depth0pt width0pt #1 \fboxsep}
\newcommand*\bmarkeq{\stepcounter{markeq}%
  \tikz[remember picture]\node(startframe-\themarkeq){\pstrut{height}};%
  \kern\fboxsep}
\newcommand*\emarkeq{\kern\fboxsep
  \begin{tikzpicture}[remember picture,overlay]
    \node (endframe-\themarkeq){\pstrut{depth}};
    \draw[,red,opacity=0.8] (startframe-\themarkeq.north) 
      rectangle (endframe-\themarkeq.south);
  \end{tikzpicture}%
}


\begin{document}


\begin{align*}
\ce{K_a $\times$ K_b} &= \ce{K_w}\\
-\log(\ce{K_a $\times$ K_b}) &= -\log\ce{K_w}\\
 -( \log(\ce{K_a}) + \log(\ce{K_b}) ) &= -\log\ce{K_w} & \text{(Using log law for LHS.)} \\
 - \log(\ce{K_a}) - \log(\ce{K_b}) &= -\log\ce{K_w}\\
\bmarkeq\ce{pK_a} + \ce{pK_b} &= \ce{pK_w}\\
&=14.00 \text{ (at \SI{25}{\celsius})}\emarkeq
\end{align*}


\end{document}

在此处输入图片描述

在此处输入图片描述

答案2

\Aboxed这是模仿mathtools包裹：

\documentclass{article}
\usepackage[version=3]{mhchem}% http://ctan.org/pkg/mhchem
\usepackage{calc}% http://ctan.org/pkg/calc
\usepackage{textcomp}% http://ctan.org/pkg/textcomp
\usepackage{siunitx}% http://ctan.org/pkg/siunitx

\begin{document}

\newlength{\mylen}% Length of widest element on left of &
\settowidth{\mylen}{$\displaystyle \ce{pK_a} + \ce{pK_b}$}
\addtolength\mylen{\fboxsep}%
\addtolength\mylen{\fboxrule}%

\begin{align*}
  \ce{K_a $\times$ K_b} &= \ce{K_w} \\
  -\log(\ce{K_a $\times$ K_b}) &= -\log\ce{K_w}\\
  -( \log(\ce{K_a}) + \log(\ce{K_b}) ) &= -\log\ce{K_w} & \text{(Using log law for LHS.)} \\
  - \log(\ce{K_a}) - \log(\ce{K_b}) &= -\log\ce{K_w}\\
 \kern\mylen & \kern-\mylen\fbox{$%
   \begin{array}{@{}l@{}}%
     \ce{pK_a} + \ce{pK_b} = \ce{pK_w} \\[\jot]%
     \phantom{\ce{pK_a} + \ce{pK_b}} = 14.00 \text{ (at \SI{25}{\textcelsius})}
 \end{array}$}
\end{align*}

\end{document}

在 align* 中强调两个等式

答案3

你也可以使用empheq包。例如

\begin{empheq}[box=\fbox]{align}
        a&=b\\
        E&=mc^2 + \int_a^b x dx
\end{empheq}

将产生以下输出： 在此处输入图片描述

更多信息请访问加拿大运输安全局或pdf 文档包的empheq。

编辑：似乎这个包只允许装箱所有对齐环境，而不允许装箱最后两行。但我不确定。请注意，我不会因为这个答案很简单而删除它。

答案4

这是一个变体这个答案那：

  • 不依赖运气1来正确查看（尝试inner sep=0在选项中设置\node，打印每个 TikZ 图片的参考点，或者简单地将\vrule第二个代码示例中的宽度更改为非零值1pt，你就会看到:-);

  • 尊重第一个方框线的高度和最后一个方框线的深度（这是棘手的部分！）；

  • 允许人们调整六个有趣的长度（四个在框架内，两个在框架外），如下所示：

\setlength{\boxPartOfAlignOuterBeforeSep}{...}%
\setlength{\boxPartOfAlignOuterAfterSep}{...}%
\setlength{\boxPartOfAlignBeforeSep}{...}%
\setlength{\boxPartOfAlignAfterSep}{...}%
\setlength{\boxPartOfAlignLeftSep}{...}%
\setlength{\boxPartOfAlignRightSep}{...}%

以下是代码：

\documentclass{article}
\usepackage{lmodern}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{mathtools}
\usepackage{mhchem}
\usepackage{siunitx}
\usepackage{lipsum}
\usepackage{tikz}
\usetikzlibrary{tikzmark}

\newcounter{markeq}

% Spacing above the top rule and below the bottom rule of our frames
\newlength{\boxPartOfAlignOuterBeforeSep}
\newlength{\boxPartOfAlignOuterAfterSep}

% Spacing inside the frames
\newlength{\boxPartOfAlignBeforeSep}
\newlength{\boxPartOfAlignAfterSep}
\newlength{\boxPartOfAlignLeftSep}
\newlength{\boxPartOfAlignRightSep}

\newcommand*{\bmarkeq}{%
  \noalign{%
    \nointerlineskip
    \kern
      \dimexpr \boxPartOfAlignOuterBeforeSep + \boxPartOfAlignBeforeSep
               + \jot \relax
    \vbox to 0pt
      {\hbox to \hsize{\tikzmark{aboveLine-\themarkeq}\hss}\vss}%
    \nointerlineskip}%
  \tikz[remember picture] \coordinate (before-\themarkeq) {};%
}

\newcommand*{\emarkeq}{%
  \tikz[remember picture] \coordinate (after-\themarkeq) {};%
  %
  \begin{tikzpicture}[remember picture, overlay]
    \coordinate (upperLeftCorner) at
      ([shift={(-\boxPartOfAlignLeftSep,\boxPartOfAlignBeforeSep)}]
       before-\themarkeq |- {pic cs:aboveLine-\themarkeq});

    \coordinate (lowerRightCorner) at
      ([shift={(\boxPartOfAlignRightSep,-\boxPartOfAlignAfterSep)}]
       after-\themarkeq |- {pic cs:belowLine-\themarkeq});

    \draw[red,opacity=0.8] (upperLeftCorner) rectangle (lowerRightCorner);
  \end{tikzpicture}%
  %
  % Insert an empty line in the alignment in order to be able to put vertical
  % material before it (in particular a zero height, zero depth \vbox
  % containing a \tikzmark that tells us where the bottom of the just-finished
  % line is located).
  \\
  \noalign{%
    \nointerlineskip
    \vbox to 0pt{\hbox to \hsize{\tikzmark{belowLine-\themarkeq}\hss}\vss}%
    \stepcounter{markeq}%
    \nointerlineskip
    % Insert “after skip” and compensate for the empty line (maybe imperfect?)
    \kern \dimexpr \boxPartOfAlignAfterSep + \boxPartOfAlignOuterAfterSep
                   -\baselineskip + \jot \relax}%
  \null\hfill                                   % this is the empty line
}

% Test material that gets repeated in every align* env (used to make the
% repeated examples shorter).
\newcommand*{\startMaterial}{%
  \ce{K_a $\times$ K_b} &= \ce{K_w}\\
-\log(\ce{K_a $\times$ K_b}) &= -\log\ce{K_w}\\
 -( \log(\ce{K_a}) + \log(\ce{K_b}) ) &= -\log\ce{K_w} & \text{(Using log law for LHS.)} \\
 - \log(\ce{K_a}) - \log(\ce{K_b}) &= -\log\ce{K_w}\\
\bmarkeq\ce{pK_a} +}

\begin{document}
\setlength{\boxPartOfAlignOuterBeforeSep}{0pt}%
\setlength{\boxPartOfAlignOuterAfterSep}{0pt}%
\setlength{\boxPartOfAlignBeforeSep}{0pt}%
\setlength{\boxPartOfAlignAfterSep}{0pt}%
\setlength{\boxPartOfAlignLeftSep}{0pt}%
\setlength{\boxPartOfAlignRightSep}{0pt}%
Let's start with tight settings (all six tunable lengths set to 0pt):
\begin{align*}
\startMaterial
  \ce{pK_b} &= \ce{pK_w} \\
            &= 14.00 \text{ (at \SI{25}{\celsius})}\emarkeq
\end{align*}
Text after the alignment. \lipsum[1][1-3]

Same thing with lines following the boxed line(s):
\begin{align*}
\startMaterial
  \ce{pK_b} &= \ce{pK_w}\\
            &= 14.00 \text{ (at \SI{25}{\celsius})}\emarkeq\\
            &= \text{whatever}
\end{align*}

{%
\setlength{\jot}{10pt}%
Same thing with more spacing between two consecutive lines of the alignment
(\verb|\jot| set to \verb|10pt|):
\begin{align*}
\startMaterial
  \ce{pK_b} &= \ce{pK_w}\\
            &= 14.00 \text{ (at \SI{25}{\celsius})}\emarkeq\\
            &= \text{whatever}
\end{align*}%
}
\lipsum[2][1-8]                 % fill the first page (for the screenshots...)

The height of the first boxed line and the depth of the last boxed line are
perfectly respected by our frame:
\begin{align*}
  \startMaterial
  \vrule width 0.4pt height 20pt depth 0pt\relax
  \ce{pK_b} &= \ce{pK_w} \\
            &= \vrule width 0.4pt height 0pt depth 10pt\relax
               14.00 \text{ (at \SI{25}{\celsius})}\emarkeq\\
            &= \text{whatever}
\end{align*}

\setlength{\boxPartOfAlignOuterBeforeSep}{3pt}%
\setlength{\boxPartOfAlignOuterAfterSep}{3pt}%
\setlength{\boxPartOfAlignBeforeSep}{3pt}%
\setlength{\boxPartOfAlignAfterSep}{3pt}%
\setlength{\boxPartOfAlignLeftSep}{3pt}%
\setlength{\boxPartOfAlignRightSep}{3pt}%
Now, with all six tunable lengths set to 3pt:
\begin{align*}
  \startMaterial
  \vrule width 0.4pt height 20pt depth 0pt\relax
  \ce{pK_b} &= \ce{pK_w} \\
            &= \vrule width 0.4pt height 0pt depth 10pt\relax
               14.00 \text{ (at \SI{25}{\celsius})}\emarkeq\\
            &= \text{whatever}
\end{align*}

\setlength{\boxPartOfAlignOuterBeforeSep}{3pt}%
\setlength{\boxPartOfAlignOuterAfterSep}{6pt}%
\setlength{\boxPartOfAlignBeforeSep}{2pt}%
\setlength{\boxPartOfAlignAfterSep}{4pt}%
\setlength{\boxPartOfAlignLeftSep}{4pt}%
\setlength{\boxPartOfAlignRightSep}{8pt}%
Finally, with funky values for the six tunable lengths:\\*[1ex]\hspace*{3em}%
\begin{tabular}{@{}>{\ttfamily\textbackslash}l@{\hspace{2em}}l}
  boxPartOfAlignOuterBeforeSep & 3pt\\
  boxPartOfAlignOuterAfterSep & 6pt\\
  boxPartOfAlignBeforeSep & 2pt\\
  boxPartOfAlignAfterSep & 4pt\\
  boxPartOfAlignLeftSep & 4pt\\
  boxPartOfAlignRightSep & 8pt\\
\end{tabular}
%
\begin{align*}
  \startMaterial
  \ce{pK_b} &= \ce{pK_w} \\
            &= 14.00 \text{ (at \SI{25}{\celsius})}\emarkeq\\
            &= \text{whatever}
\end{align*}

\end{document}

第一页：

在此处输入图片描述

第二页：

在此处输入图片描述

稍有变化：

\newcommand*{\emarkeq}{%

  (...)

    \draw[blue, opacity=0.8, rounded corners]
      (upperLeftCorner) rectangle (lowerRightCorner);
  \end{tikzpicture}%

  (...)

}

可以得到：

在此处输入图片描述

脚注：

  1. inner sep或者更确切地说，基于 TikZ 节点的默认值。

相关内容