Graph Properties / Features

3. A closed path is a path that begins and ends at the same vertex.
   

   The sequence $1,2,3,1$ is a closed path because it starts and ends at vertex $1$. Miriam Briskman, CC BY-NC 4.0.

   \documentclass[border=1pt]{standalone}
   \usepackage{tikz}
   
   \tikzset{
   vertex/.style={draw, circle, very thick, minimum size=1cm},
   edge/.style={very thick}
   }
   
   \begin{document}
   
   \begin{tikzpicture}
   
   \node[vertex] (v1) at (0,0) {$1$};
   \node[vertex] (v2) at (3,0) {$2$};
   \node[vertex] (v3) at (1.5,2) {$3$};
   
   \draw[edge] (v1) -- (v2);
   \draw[edge] (v2) -- (v3);
   \draw[edge] (v3) -- (v1);
   
   \end{tikzpicture}
   
   \end{document}