How to make underbracket thinner
Excerpting from p. 14 of the user guide of the mathtools
package (highlighting added):
The user guide says that the default width of underbrackets is ca 5/18ex
= ca. 0.28ex
. The following screenshot shows expressions with underbrackets that involve the default width as well as one half, two thirds, and three quarters of the default width. Choose your favorite.
\documentclass{article}
\usepackage{mathtools} % for '\underbracket' macro
\begin{document}
\[
% default width: 5/18ex = ca 0.28ex
\underbracket{1+2+3}_{\text{default}} % default width
+\underbracket[0.140ex]{1+2+3}_{\text{tubelike}}% (1/2)default
+\underbracket[0.187ex]{1+2+3}_{\text{skinny}} % (2/3)default
+\underbracket[0.210ex]{1+2+3}_{\text{thin}} % (3/4)default
+\underbracket[0.280ex]{1+2+3}_{\text{default}} % default
\]
\end{document}
The thickness of brackets can be specified in the first optional argument of \underbracket
and \overbracket
. The default thickness is the height of $\braceld$
(in current math font).
\documentclass{article}
\usepackage{mathtools}
\begin{document}
\[
C(s) =
% use thickness 0.5pt
\underbracket[.5pt]{\frac{K_1}{s}}_{\text{forced}} +
% use default thickness
\underbracket{\frac{K_2}{s+2}+\frac{K_3}{s+4}+\frac{K_4}{s+5}}_{\text{natural}}
\]
\end{document}
You can also change the thickness of brackets once for all:
\documentclass{article}
\usepackage{mathtools}
\usepackage{xpatch}
% change default thickness of brackets to .6pt
\MHInternalSyntaxOn
\xpatchcmd\upbracketfill
{\sbox\z@{$\braceld$}\edef\l_MT_bracketheight_fdim{\the\ht\z@}}
{\edef\l_MT_bracketheight_fdim{.6pt}}
{}{\fail}
\xpatchcmd\downbracketfill
{\sbox\z@{$\braceld$}\edef\l_MT_bracketheight_fdim{\the\ht\z@}}
{\edef\l_MT_bracketheight_fdim{.6pt}}
{}{\fail}
\MHInternalSyntaxOff
\begin{document}
\[
C(s) =
\underbracket{\frac{K_1}{s}}_{\text{forced}} +
% use default thickness
\overbracket{\frac{K_2}{s+2}+\frac{K_3}{s+4}+\frac{K_4}{s+5}}^{\text{natural}}
\]
\end{document}