I want to change original header of book in the latex,
for even page number :
From
become
(Page number on the black square with shadow and add line below the chapter name & page number)
for odd page number :
from
become
(Page number on the black square with shadow and add line below the subchapter name & page number)
My code is :
\documentclass[a4paper,12pt,twoside]{book}
\usepackage[left=3.00cm, right=2.00cm, bottom=2.00cm, top=2.00cm]{geometry}
\usepackage[Lenny]{fncychap}
\usepackage{amsmath}
\usepackage{newtxtext,mathptmx}
\begin{document}
\chapter{CHAPTER TEST}
\section{TEST1}
$$\Gamma(n)=\int\limits_0^\infty x^{n-1}e^{-x}dx$$
This is Gamma function.
\subsection{SUBTEST}
\newpage
\section{TEST2}
blablabla
\newpage
\section{TEST3}
\end{document}
How to do that? Please help me. Thank you.

\[...\]instead of$$...$$. – Sebastiano Dec 18 '18 at 07:44$$...$$it is the old syntax. Have you seen the link on my previous comment? – Sebastiano Dec 18 '18 at 08:00$$..$$in tex documents. As you are not using tex, but latex, you should use\[...\]– samcarter_is_at_topanswers.xyz Dec 18 '18 at 10:18