%%
%% The LaTeX Companion, 3ed
%%
%% Example 11-8-3 on page II-211 in "Mathematical symbol classes".
%%
%% Copyright (C) 2022 Frank Mittelbach
%%
%% It may be distributed and/or modified under the conditions
%% of the LaTeX Project Public License, either version 1.3c
%% of this license or (at your option) any later version.
%%
%% See https://www.latex-project.org/lppl.txt for details.
%%

\documentclass{tlc3examargin}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{135.0pt}

  % Shorten the vertical size of the example ...
  \AtBeginDocument{%
    \setlength\abovedisplayskip{.2\abovedisplayskip}%
    \setlength\belowdisplayskip{.1\belowdisplayskip}%
  }

%StartShownPreambleCommands
\thinmuskip=10mu \medmuskip=15mu \thickmuskip=20mu
%StopShownPreambleCommands

\begin{document}
\[ a \Bigl( \sum x \Bigr) \neq a \left( \sum x \right) \]
\[ \sin(x^2),x            \neq \sin\left(x^2\right),x  \]
\end{document}
