[Tex/LaTex] Multiple Chapter Styles in same Document

sectioning

I have a newbie question: I have a two-part document and I would like to use a different Chapter styling for each one; I've looked up in this database and "googled" it, to no avail.
Any idea?
Thank you!

Best Answer

Does this help you? The particular chapter styles chosen are random and lousy. If you want to change section, subsection, part styles you would likewise redefine them.

\documentclass[10pt]{book}
\usepackage{titlesec}

%original definition
\titleformat{\chapter}[display]
  {\normalfont\bfseries\filcenter}{\LARGE\thechapter}{1ex}
  {\titlerule[2pt]\vspace{2ex}}[\vspace{1ex}{\titlerule[2pt]}]
\titleformat{name=\chapter,numberless}[display]
  {\normalfont\LARGE\bfseries\filcenter}{}{1ex}
  {\vspace{2ex}}[\vspace{1ex}]
%end of original definition

\begin{document}

\part{A Part}

\chapter{A chapter}
\chapter{Another chapter}

%another definition
\titleformat{\chapter}[display]
{\normalfont\huge\bfseries}{\filcenter\underline{\MakeUppercase{{\chaptertitlename}}\ \thechapter}}{20pt}{\Huge}
%end of other definition

\part{A second Part}

\chapter{Three plus Three}
\chapter{Four plus Four}

\end{document}

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