# Redefined pagenumbering with \cfoot does not show up in ToC

For my thesis I'm adding an 'Addendum' with extra pages. I want the pages in the addendum being numbered as 'A1'. In this I succeeded using fancyhdr and \cfoot. Unfortunately in my table of contents this shows up as '1' instead of A1. Can somebody help? Thanks in advance. Here is my code and output:

\documentclass[11pt,a4paper,oneside]{book}
\usepackage{graphicx,xcolor,textpos}
\usepackage{helvet}
\usepackage[font=small,labelfont=bf]{caption}
\usepackage{dirtytalk}
\usepackage{float}
\usepackage{fancyhdr}
\begin{document}
\rmfamily
\renewcommand{\rmdefault}{phv} % Arial
\renewcommand{\sfdefault}{phv} % Arial
\setcounter{page}{0}
\pagenumbering{roman}
{\pagestyle{plain}
\tableofcontents
\chapter{chapter 1}
…
\thispagestyle{fancy}
\fancyhf{}
\pagenumbering{arabic}
\cfoot{A.\thepage}
\end{document}


Output:

• Welcome to TeX.SE! What document class are you using? It would be more likely someone can come up with an answer if you provided a minimal working example (MWE). – Troy May 24 '18 at 12:54
• I'm sorry I'm new to this :). I have edited my post with more code, hope this is sufficient. Thanks in advance! – Koen May 24 '18 at 13:07
• There is a spurious "{" before \pagestyle{plain} – Raoul Kessels May 24 '18 at 13:50

You have to redefine the command \thepage. Instead of issuing \pagenumbering{arabic}, use:
%\pagenumbering{arabic}

Then, the page numbers will appear as A.<page> in both the page and the table of contents.