Parabollic

PB.tex

\documentclass[titlepage]{amsbook}
\usepackage[utf8]{inputenc}
\usepackage[english]{babel}
\usepackage{amsbsy,amsmath,amssymb}
\usepackage{tikz}    

\begin{document}
\thispagestyle{empty}
\begin{center}
\begin{tikzpicture}
\pgfmathsetmacro{\H}{6} 
\pgfmathsetmacro{\inctime}{.375}
\foreach \i in {0,\inctime,...,\H} {
\draw[red!40!orange, thick, opacity=.4] (\H-\i,0) -- (0,\i) -- (\i-\H,0);
\draw[red!40!orange, thick, opacity=.4] (\H-\i,0) -- (0,-\i) -- (\i-\H,0);
}
\end{tikzpicture}
\end{center}
\end{document}