Remove the Chapter number, but keep chapter number in the formula

Question

I have a problem just as the following picture. I want to remove the chapter number in appendix, but keep the number in the formula. I have tried many times.

Answer 1

If you are using a KOMA-Script class like scrbook or scrreprt you can redefine \chapterformat (and \chaptermarkformat and \thesection) inside \appendix:

\documentclass{scrbook}

\usepackage[ngerman]{babel}
\usepackage{xpatch}
\apptocmd\appendix{\renewcommand*{\chapterformat}{}\let\chaptermarkformat\chapterformat\renewcommand*{\thesection}{\arabic{section}}}{}{}

\begin{document}
\chapter{Test}
\appendix
\chapter{Anhang}
\section{Lange Formeln}
\begin{equation}
  f(x)=a+b+c+d+e+f+g+h+i+j+k+l+m
\end{equation}

\end{document}

But have a look at: »Wie setzt man korrekt einen Anhang?« (in German, but it seems the OP does understand German).