\documentclass[12pt,a4paper]{book}
\usepackage{geometry}
\geometry{a4paper, top=2cm, left=2.5cm, right=2.5cm, bottom=2cm, includehead, includefoot}
\usepackage{subcaption,caption}
\usepackage{xcolor,graphicx,tikz,pdfpages}
\usetikzlibrary{arrows,shapes}
\usepackage{array}
\usepackage[framemethod=TikZ]{mdframed}
\usepackage{fourier}
\usepackage{relsize}
\usepackage{empheq}
\usepackage[colorlinks=true,linkcolor=red,]{hyperref}
\usepackage{mathrsfs}
\usetikzlibrary{shapes,decorations}
\usepackage{amssymb,mathtools,amsthm,enumerate,bigints}
\usepackage{multicol}
\usepackage{ragged2e}
\usepackage{float}
\usepackage{pgfplots}
\pgfplotsset{width=8cm,compat=1.14}
%===================================================
\usepackage{fancyhdr}
\pagestyle{fancy}
\fancyhead {}
\renewcommand{\headrulewidth}{0.01pt}
\fancyhead[LO,RE]{\leftmark}
\fancyhead[RO,LE]{\thepage}
\fancyfoot{}
\include{otherfiles/styy}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%ù
\newcommand\norm[1]{\left\lVert#1\right\rVert}
\newcommand{\nequiv}{\not\equiv}
\usepackage{makeidx}
\makeindex
\usepackage[totoc]{idxlayout}
\begin{document}
\include{otherfiles/pagegarde}
\pagecolor{white}
\setcounter{tocdepth}{1}
\pagenumbering{roman}
\large
\tableofcontents
\include{otherfiles/Intro}
\pagenumbering{roman}
\pagestyle{fancy}
%======================================================
\include{Chap1}
\include{Chap2}
\include{Chap3}
\include{otherfiles/biblio}
\selectlanguage{arabic}
\pagestyle{empty}
\include{otherfiles/Notation}
\printindex
%======================================================
\end{document}
