答案1
您可以加载该xcolor
包并使用\colorbox
宏(请参阅 xcolor 包的用户指南来决定突出显示的颜色):
\documentclass{article}
\usepackage[dvipsnames]{xcolor} % for 'CornflowerBlue'
\usepackage{newtxtext,newtxmath,amsmath,bm}
\newcommand\cbox[1]{\colorbox{CornflowerBlue}{$#1$}}
\begin{document}
\noindent
Then we expand the exponential as a series and have
\begin{align*}
&= \gamma^0 \sum_{n=0}^\infty \frac{1}{n!}
\Bigl[i\frac{\alpha}{2}\gamma^5\Bigr]\gamma^0.
\intertext{With $\gamma^0\gamma^0=\bm{1}_4$, we can wrap every
single $\gamma^5$ into $\gamma^0$.}
&= \sum_{n=0}^\infty \frac{1}{n!}
\Bigl[\cbox{\gamma^0} i\frac{\alpha}{2}\gamma^5\cbox{\gamma^0}\Bigr].
\end{align*}
\end{document}