列出方程中的变量

Question

我的代码看起来太糟糕了

When monochromatic light is shone through a solution of iron, Beer's law states that 

$$ A = \varepsilon l c $$
\begin{tabular}{l}
      Where $A$ is amount of light absorbed \\
      \quad \quad  \quad $\varepsilon$ is the molar absorbance coefficient, which varies with wavelength,\\
      \quad \quad  \quad but not with concentration\\
      \quad  \quad \quad $l$ is the thickness of the sample

\end{tabular}

可以改善吗？

Answer 1

请查看为什么 \[ ... \] 比 $$ ... $$ 更可取？，变量的描述可以用description或在列表中进行itemize。

从个人角度来看，我宁愿使用\ell而不是l作为方程标识符。

\documentclass{article}

\usepackage{mathtools}

\begin{document}
When monochromatic light is shone through a solution of iron, Beer's law states that 

\[ A = \varepsilon l c \]

\noindent where
\begin{description}
\item  $A$ is amount of light absorbed 
\item  $\varepsilon$ is the molar absorbance coefficient, which varies with wavelength,\\
  but not with concentration
\item  $l$ is the thickness of the sample
\end{description}


\end{document}

另一个（更好的？）解决方案，可以对列表参数进行更精细的控制，具有更好的视觉吸引力，但这实际上是一个品味问题。

\documentclass{article}

\usepackage{enumitem}
\usepackage{mathtools}

\begin{document}
When monochromatic light is shone through a solution of iron, Beer's law states that 

\[ A = \varepsilon \ell c \]

\noindent where
\begin{description}
\item $A$   is amount of light absorbed 
\item  $\varepsilon$ is the molar absorbance coefficient, which varies with wavelength,\\
  but not with concentration
\item  $\ell$ is the thickness of the sample
\end{description}


\noindent where
\begin{description}[labelindent=10pt,labelsep=10pt]
\item[$A$]   is amount of light absorbed 
\item[$\varepsilon$] is the molar absorbance coefficient, which varies with wavelength,\\
  but not with concentration
\item[$\ell$] is the thickness of the sample
\end{description}

\end{document}

Answer 2

另一种选择是使用(d)cases环境：

代码如下：

\documentclass{article}
\usepackage{mathtools}
\begin{document}

  When monochromatic light is shone through a solution of iron, Beer's law states that
  \[ A = \varepsilon l c ,\quad
    \text{where }\quad
    \begin{dcases*}
        A& is amount of light absorbed \\
        \varepsilon& is the molar absorbance coefficient, which varies \\
                   & with wavelength but not with concentration\\
        l& is the thickness of the sample
  \end{dcases*}
  \]

\end{document}

当然，你也可以使用普通cases环境，但我更喜欢dcases更喜欢数学工具包裹。

Answer 3

两个棘手的例子（您的代码在开头）：

\documentclass{article}
\begin{document}

When monochromatic light is shone through a solution of iron, Beer's law states that 

$$ A = \varepsilon l c $$
\begin{tabular}{l}
      Where $A$ is amount of light absorbed \\
      \quad \quad  \quad $\varepsilon$ is the molar absorbance coefficient, which varies with wavelength,\\
      \quad \quad  \quad but not with concentration\\
      \quad  \quad \quad $l$ is the thickness of the sample
\end{tabular}

\bigskip

When monochromatic light is shone through a solution of iron, Beer's law states that 
\[
 A = \varepsilon l c 
\]
 Where $A$ is amount of light absorbed 

\noindent\hangindent3em\hangafter0
      $\varepsilon$ is the molar absorbance coefficient, which varies with wavelength,\\
     but not with concentration\\
       $l$ is the thickness of the sample



When monochromatic light is shone through a solution of iron, Beer's law states that 
\[
 A = \varepsilon l c 
\]
Where $A$ is amount of light absorbed \\
 \hspace*{3em}%     
\begin{tabular}{l}
$\varepsilon$ is the molar absorbance coefficient, which varies with wavelength,\\
       but not with concentration\\
       $l$ is the thickness of the sample
\end{tabular}

\end{document}

Answer 4

我不确定这是否有帮助，但我通常会这样做：

\documentclass{article}    
\usepackage{amsmath}    

\begin{document}
When monochromatic light is shone through a solution of iron, Beer's law states that:

\begin{equation*} % The starred version avoid the automatic number.
 A = \varepsilon l c
 \end{equation*} 

\noindent Where:\\ 
$A$ is amount of light absorbed, \\
$\varepsilon$ is the molar absorbance coefficient, which varies with wavelength, but not with concentration, and\\
$l$ is the thickness of the sample.
\end{document}

我使用amsmath带星号的环境版本equation，它产生的结果是相同的，equation但方程式的数量不同。我不使用该tabular环境，对齐非常简单。它对你有用吗？