# Local fullwidth environment in symmetric document with margin

In a symmetric twoside document with 5cm margin on the outer side of each page, I want to create an enviroment where I can place locally a piece of text of full page width. Any solution that I have tried so far does not create the desired effect. For example the custom narrow environment shown in the MWE adds margin on the current page, but when the text goes to the next page, it vanishes at the edge.

\documentclass[a4paper,twoside,11pt,symmetric]{book}
\usepackage[no-math,cm-default]{fontspec}
\usepackage{xunicode}
\defaultfontfeatures{Mapping=tex-text,Scale=MatchLowercase}
\setmainfont[Mapping=tex-text,Numbers=Lining,Scale=1.0,BoldFont={Times New Roman Bold}]{Times New Roman}
\defaultfontfeatures{Ligatures=TeX}
\usepackage{lipsum}
\usepackage[inner=2.00cm, top=3.00cm, bottom=2.00cm]{geometry}
\geometry{textwidth=12cm,marginparsep=5mm,marginparwidth=5cm}

\newenvironment{narrow}[2]{%
\begin{list}{}{%
\setlength{\leftmargin}{#1}%
\setlength{\rightmargin}{#2}}%
\item[]}{\end{list}}

\begin{document}
\chapter{Chapter 1}
\section{Section 1}
\lipsum\lipsum
\begin{narrow}{0cm}{-5cm}
\lipsum
\lipsum
\lipsum
\end{narrow}
\end{document}


Is it possible to adjust the textwidth no matter if the page is even or odd?

• The changepage package defines an adjustwidth environment. – Bernard Nov 2 '18 at 22:24
• I used adjustwidth  but the problem with the next page remains. It's because it changes the left and right margins. I want to be able to change locally the inner and outer margins of the even and odd pages. – mac Nov 2 '18 at 22:29
• I didn't understand what a symmetric document means. You do want a piece of text which extends on the full paper width, or do I misunderstand? – Bernard Nov 2 '18 at 22:45
• Yes that's right. Without getting the result as shown in the pictures. – mac Nov 2 '18 at 23:02
• You didn't explain what ‘symmetric’ docume nt means. – Bernard Nov 2 '18 at 23:16