ctex问题源文件如下\documentclass[a4paper,12pt]{article}\begin{document}\ldots when Einstein introduced his formula\begin{equation} \label{1}e = m \cdot c^2 \;,\end{equation}which is at the same time the most widely known andthe least well unde

ctex问题
源文件如下
\documentclass[a4paper,12pt]{article}
\begin{document}
\ldots when Einstein introduced his formula
\begin{equation} \label{1}
e = m \cdot c^2 \;,
\end{equation}
which is at the same time the most widely known and
the least well understood physical formula
\end{document}
请问公式后面\;有什么用?

\cdot 表示乘号, \；表示空格.