[Tex/LaTex] How to make large brace and parenthesis thinner

Question

A MWE is as follows:

\documentclass{amsart}

\begin{document}
\Huge
We have
\[
f(x)=
\begin{cases}
2x^{2018}+9&x<2018\\
3x+2018&x\geq 2018.
\end{cases}
\]
And we also have
\[
\left(
\begin{array}{cc}
 x   &m  \\
 y   &n  \\
 x   &m  \\
 y   &n
\end{array}
\right).
\]

\end{document}

As you see in the PDF, the large brace and parenthesis are very thick.

Then my question is: How to make large brace and parenthesis be thinner? Any help is welcome!

Answer 1

You could (ab)use \scalebox.

\documentclass{amsart}
\usepackage{graphicx}
\begin{document}
\Huge
We have
\[
f(x)=
\scalebox{0.5}[1]{$\displaystyle
\left\{\scalebox{2}[1]{$\displaystyle\begin{array}{ll}
2x^{2018}+9&x<2018\\
3x+2018&x\geq 2018.
\end{array}$}\right.$}
\]
And we also have
\[
\scalebox{0.5}[1]{$\displaystyle
\left(\scalebox{2}[1]{$\displaystyle
\begin{array}{cc}
 x   &m  \\
 y   &n  \\
 x   &m  \\
 y   &n
\end{array}$}
\right)$}.
\]
\end{document}

If you want to use that very often, you may define your own environments for that.

\documentclass{amsart}
\usepackage{graphicx}
\usepackage{environ}
\NewEnviron{thincases}{\scalebox{0.5}[1]{$\displaystyle
\left\{\scalebox{2}[1]{\setlength{\arraycolsep}{6pt}% <- I did not look up the "correct" value
$\displaystyle\begin{array}{ll}
\BODY
\end{array}$}\right.$}}%}
\NewEnviron{thinpmatrix}{\scalebox{0.5}[1]{$\displaystyle
\left(\scalebox{2}[1]{$\displaystyle
\begin{matrix}
\BODY
\end{matrix}$}
\right)$}}
\begin{document}
\Huge
We have
\[
f(x)=
\begin{thincases}
2x^{2018}+9&x<2018\\
3x+2018&x\geq 2018.
\end{thincases}
\]
And we also have
\[
\begin{thinpmatrix}
 x   &m  \\
 y   &n  \\
 x   &m  \\
 y   &n
\end{thinpmatrix}
\]
\end{document}