\documentclass{article} \usepackage[UTF8]{ctex} \usepackage{fancyhdr} \usepackage{graphicx} \usepackage{amsmath} \usepackage{tasks} \usepackage{geometry} \usepackage{float} \usepackage{tikz} \geometry{a4paper,left=2cm,right=2cm,top=1.5cm,bottom=1.5cm} \pagestyle{fancy} \lhead{} \chead{} \rhead{} \lfoot{} \cfoot{} \rfoot{\thepage} \renewcommand{\headrulewidth}{0.4pt} \renewcommand{\footrulewidth}{0.4pt} \linespread{1.35} \begin{document} \begin{tikzpicture}[scale=1.5,line width=1pt] %A-D-C \draw[dashed,fill=blue!20](1.414,0,0)node[below]{$A$}--(-1.414,0,0)node[below]{$D$}--(-1.414,2,0)node[right]{$C$}; %P-D \draw[dashed,red](0,0,1.414)--(-1.414,0,0); %P-A-B-C-P-B \draw(0,0,1.414)node[above]{$P$}--(1.414,0,0)--(1.414,2,0)node[below]{$B$}--(-1.414,2,0)--(0,0,1.414)--(1.414,2,0); \end{tikzpicture} \end{document}