答案1
此解决方案使用 tikz 绘制气泡。气泡包含在对齐中,而不是被覆盖。
如果您打算经常这样做,您可以尝试查找或创建一个 tikz“形状”。
\documentclass{article}
\usepackage{amsmath}
\usepackage{mathstyle}% for \currentmathstyle
\usepackage{tikz}
\makeatletter
\newcommand{\mymathbox}[1]{%
\tikz[baseline=(temp.base)]{%
\node(temp){$\m@th\currentmathstyle#1$};
\draw (temp.south)+(2pt,0pt) -- +(0pt,-1ex) -- +(-2pt,0pt)% all offsets from (temp.south)
[rounded corners] -- (temp.south west) -- (temp.north west) -- (temp.north east) -- (temp.south east)
[sharp corners] -- cycle;
}%
}
\makeatother
\begin{document}
\begin{equation*}
\mymathbox{\frac{d}{dt}I(t)} = \frac{d}{dt}I(t)
\end{equation*}
\end{document}