如何使用大小可变的鱼叉来强调数学？

Question

我是 LaTeX 的新用户。我想用符号在数学问题的答案下划线\rightharpoondown。如果可能的话，我想要一个\rightharpoondown可变大小的符号，如下图所示。我该如何实现呢？

Answer 1

这里有三个宏：(1) 用钩子划下划线，(2) 用椭圆圈出答案，(3) 在右下角放置两条对角线。请注意，我使用该siunitx包来编写答案；该包用于正确编写值的单位。

\documentclass[border=5pt]{standalone}

\usepackage{amsmath}
\usepackage{siunitx}
\usepackage{tikz}
\usetikzlibrary{calc}
\usetikzlibrary{shapes.geometric}

\newcommand{\answer}[1]{
\tikz[baseline=(answer.base)]{
\node[inner sep=3pt] (answer) {#1};
\draw[line cap=round] (answer.south west) -- (answer.south east)  -- ++(-0.1,-0.1); 
}} 

\newcommand{\answercircled}[1]{
\tikz[baseline=(answer.base)]{
\node[ellipse,draw,inner sep=3pt] (answer) {#1};
}} 

    \newcommand{\answerside}[1]{
\tikz[baseline=(answer.base)]{
\node[inner sep=3pt] (answer) {#1};
\draw[double, double distance=2pt] ($(answer.south east) + (45:0.2)$) -- ($(answer.south east) - (45:0.2)$);
}} 

\begin{document}
$x = \answer{\SI{5}{Volts}} = \answercircled{\SI{5}{Volts}}= \answerside{\SI{5}{Volts}}$

\end{document}

结果是

Answer 2

在我教授的榜样之后，再次感谢Frédéric。

 \documentclass[border=5pt]{standalone}

 \usepackage{amsmath}
 \usepackage{siunitx}
 \usepackage{tikz}
 \usepackage{color}

 \usetikzlibrary{calc}
 \usetikzlibrary{shapes.geometric}

 \newcommand{\answer}[1]{
 \tikz[baseline=(answer.base)]{
 \node[inner sep=3pt] (answer) {#1};
 \color{red}
 \draw[line width=1pt,color=red][line cap=round] {[rounded corners](answer.south west) -- (answer.south east) } -- ++(-0.5,-0.5);
 }} 

 \begin{document}

 $x = \answer{\SI{5.977}{Volts}}$

 \end{document}

结果是