I would like make a fancy chapter like the figure.

\documentclass[12pt,a4paper]{book}

\usepackage{lmodern}
\usepackage{titlesec}
\usepackage{microtype}
\usepackage{tikz}

\titleformat{\chapter}[display]
{\normalfont\bfseries\color{black}}
{%\filleft%
\begin{tikzpicture}
\node[
outer sep=-10pt,
text width=2.5cm,
minimum height=3cm,
fill=black,
font=\color{white}\fontsize{80}{90}\selectfont,
align=center
] (num) {\thechapter};
\node[
rotate=0,
anchor=south,
font=\color{black}\Large\normalfont
] at ([yshift=43pt,xshift=30]num.west)  {\textls[180]{\textsc{\chaptertitlename}}};
\end{tikzpicture}%
}
{-90pt}
{\titlerule[2.5pt]\vskip3pt\titlerule\vskip4pt\LARGE\sffamily \raggedright }

\begin{document}
\chapter{The Singular Sturm-Liouville Problems in Spectral Parameter}

\end{document}



that produces this one

How can I produce the chapter like the First Figure?

• Please do not ask questions twice! Better is to edit your first question tex.stackexchange.com/questions/501778/fancy-chapter-style with needed updates to make it as clear as possible! And please -- as usual here -- make your code snippet compilable! Then we do not have to guess what you are doing ... – Mensch Aug 6 '19 at 16:36
• Please provide a complete MWE, so we can provide help. I have tried to compile your code and didn't work. – Mauramz Aug 6 '19 at 19:01
• Now, the code is compiling, thanks for your remark. – Daniel Borin Aug 8 '19 at 9:00

Is this what you want?

\documentclass[12pt,a4paper]{book}
\usepackage{lipsum} % dummy text

\usepackage{lmodern}
\usepackage[explicit]{titlesec}
\usepackage{microtype}
\usepackage{tikz}

\titleformat%
{\chapter}[hang]%
{\bfseries}{%
\begin{minipage}[t]{0.3\linewidth}
\vspace{0pt}% do not remove
\begin{tikzpicture}
\node[
outer sep=0pt,
text width=2.5cm,
minimum height=2.5cm,
fill=black,
font=\color{white}\fontsize{80}{90}\selectfont,
align=center
] (num) {\thechapter};
\node[
outer sep=0pt,
inner sep=0pt,
anchor=south,
font=\color{black}\Large\normalfont
] at ([yshift=3pt]num.north) {\textls[180]{\textsc{\chaptertitlename}}};
\end{tikzpicture}
\end{minipage}%
}
{0pt}%
{%
\begin{minipage}[t]{.7\linewidth}%
\vspace{2pt} % do not remove
\rule{\linewidth}{2.5pt}\\\vskip -1.75\baselineskip%
\rule{\linewidth}{.7pt}\vskip 5pt
{\LARGE\raggedright\textsf{#1}}
\end{minipage}%

}

\begin{document}
\chapter{The Singular Sturm-Liouville Problems in Spectral Parameter}
\lipsum[1]
\end{document}

• That is right, i compileted and works just fine, Thank you for the Help – Daniel Borin Aug 22 '19 at 0:02