Record some code

Equations share the same numbering with theorems with ntheorem package

\newtheorem{thm}{Theorem}[section]
\numberwithin{equation}{section}
\makeatletter
\let\c@equation\c@thm
\makeatother

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change the font of sections, subsections, chapter to \sf
\usepackage{sectsty}
\allsectionsfont{\sffamily}