%%
%% The LaTeX Companion, 3ed
%%
%% Example 11-4-29 on page II-176 in "amsmath, accents, mathdots --- Various accents".
%%
%% 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{.4\abovedisplayskip}%
    \setlength\belowdisplayskip{.8\belowdisplayskip}%
  }

%StartShownPreambleCommands
  \newcommand\accsample[1]{\dot{#1} \; \ddot{#1} \;
     \mathring{#1} \; \acute{#1} \; \grave{#1} \; \hat{#1}
     \; \check{#1} \; \breve{#1} \; \bar{#1} \; \tilde{#1}
     \quad \vec{#1} \; \widehat{#1} \; \widetilde{#1}}
%StopShownPreambleCommands

\begin{document}
  \[ \accsample{x} \]     \[ \mathbf{\accsample{y}} \]
  \[ \hat{\mathbf{C}} \simeq \mathbf{\hat{C}}  \]
\end{document}