圈出方程式中的兩項，並透過乳膠中的箭頭將它們連接起來

Question

我想知道是否可以在方程式中做類似的事情。

我的程式碼在這裡

\documentclass[12pt]{article}
%\usepackage[english]{babel}
%\usepackage{amsmath,amsthm}
 %\usepackage{amsfonts}
 \usepackage[T1]{fontenc}
\usepackage{mathpazo}
\usepackage{tikz}         
 \usetikzlibrary{arrows}

 \newcommand{\tikzmark}[2]{%
\tikz[remember picture,baseline=(#1.base)]
\node[text=black,anchor=center,inner sep=1pt] (#1) {#2};}


 \begin{document}

$$\tikzmark{a}{a}=\tikzmark{c}{c}$$

\tikz[overlay,remember picture]{\draw[blue,thick,->] (a.north) to [bend left=45] node[anchor=south]{$=$}(c.north);}

\end{document}

我不知道底部的繪製箭頭。

Answer 1

\documentclass[12pt]{article}
 \usepackage[T1]{fontenc}
\usepackage{mathpazo}
\usepackage{tikz}         
 \usetikzlibrary{arrows}

 \newcommand{\tikzmark}[2]{%
\tikz[remember picture,baseline=(#1.base)]
\node[text=black,anchor=center,inner sep=1pt] (#1) {#2};}


 \begin{document}

\[\tikzmark{a}{a}=\tikzmark{c}{c}\]

\tikz[overlay,remember picture]{\draw[blue,thick,->]
   (a.north) to [bend left=45] node[above]{\scriptsize$=$}(c.north);}
\tikz[overlay,remember picture]{\draw[blue,thick,->]
   (a.south) to [bend right=45] node[below]{\scriptsize$=$}(c.south);}

\end{document}

Answer 2

不使用tikz：

\documentclass[12pt]{article}
\usepackage[T1]{fontenc}
\usepackage{amsmath,amssymb}

\usepackage{graphics}
\newcommand{\arroweqover}{\substack{\mathstrut \mkern7mu=\\ \scalebox{2.5}{$\mkern4mu\curvearrowright$}}}

\newcommand{\arrowequnder}{\substack{\rotatebox{180}{\scalebox{2.5}{$\mkern-4mu\curvearrowleft$}}\\ \mathstrut\mkern7mu=}}

\begin{document}
\[
 \overset{\arroweqover}{\underset{\arrowequnder}{A=c}} 
\]
\end{document}