答案1
您没有提供有关当前输入的任何线索,但通常您可以从较小的字体中选择一个分隔符,该字体将延伸到相同的高度,但更细。
\documentclass{article}
\usepackage{amsmath}
\begin{document}
xxxxx $
\left\{
\begin{aligned}
x+y&=0\\
x+2y&=0
\end{aligned}
\right.
$
xxx
\bigskip
xxxxx $\scriptscriptstyle
\left\{
\begin{aligned}
x+y&=0\\
x+2y&=0
\end{aligned}
\right.
$
xxx
\end{document}
答案2
使用 \scriptstyle 和 \scriptscriptstyle 来改变字体大小。
\documentclass[UTF8, 12pt]{article}
\usepackage{amsmath}
\setlength{\parindent}{0pt}
\renewcommand{\baselinestretch}{1.5}
\DeclareMathSizes{12}{10}{7}{5} % default size
% \textstyle, \displaystyle, \scriptstyle, \scriptscriptstyle
\begin{document}
1. XXXXXXXX $
\left\{
\begin{aligned}
x + y - 2z - 1 = 0 \\
x + 2y - z + 1 = 0
\end{aligned}
\right.
$ XXXXXXXX.
2. XXXXXXXX $
\displaystyle % 10pt
\left\{
\begin{aligned}
x + y - 2z - 1 = 0 \\
x + 2y - z + 1 = 0
\end{aligned}
\right.
$ XXXXXXXX.
3. XXXXXXXX $
\scriptstyle % 7pt
\left\{
\begin{aligned}
x + y - 2z - 1 = 0 \\
x + 2y - z + 1 = 0
\end{aligned}
\right.
$ XXXXXXXX.
4. XXXXXXXX $
\scriptscriptstyle % 5pt
\left\{
\begin{aligned}
x + y - 2z - 1 = 0 \\
x + 2y - z + 1 = 0
\end{aligned}
\right.
$ XXXXXXXX.
\end{document}