# how to put suspension points on a tikz figure

I'm want to put suspension points as in the picture above. What should I add to the code below?

\documentclass[12pt]{article}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}[roundnode/.style={circle, fill=black!70, inner sep=0pt, minimum size=1.5mm}]

\node[roundnode,label=right:{$u^{}_1$}] at (1,0) (u1) {};
\node[roundnode,label=above right:{$u^{}_2$}] at (0.78539816339,0.70710678118) (u2) {};
\node[roundnode,label=:{$u^{}_3$}] at (0,1) (u3) {};
\node[roundnode,label=above left:{$u^{}_4$}] at (-0.78539816339,0.70710678118) (u4) {};
\node[roundnode,label=left:{$u^{}_5$}] at (-1,0) (u5) {};
\node[roundnode,label=left:{$u^{}_6$}] at (-0.78539816339,-0.70710678118) (u6) {};
\node[roundnode,label=below:{$u^{}_7$}] at (0,-1) (u7) {};
\node[roundnode,label=below right:{$u^{}_n$}] at (0.78539816339,-0.70710678118) (un) {};

\draw[-] (un) -- (u1) -- (u2) -- (u3) -- (u4) -- (u5) -- (u6) -- (u7);
\end{tikzpicture}
\end{document}
• Welcome to TeX - LaTeX! By "suspension points" do you mean the dotted line? If so then \draw[dotted] or \draw[loosely dotted] is probably what you are looking for. You can add thick or similar to get larger dots. – Andrew Swann Dec 9 '18 at 17:12
• @AndrewSwann Excuse me. But I remember that this question is old. – Sebastiano Dec 9 '18 at 17:15

Slightly more complicated than nidhin's solution, add \usetikzlibrary{calc} and use

\foreach \i in {0.25,0.5,0.75}
\fill ($(un)!\i!(u7)$) circle[radius=1pt];

\documentclass[12pt]{article}
\usepackage{tikz}
\usetikzlibrary{calc}
\begin{document}
\begin{tikzpicture}[roundnode/.style={circle, fill=black!70, inner sep=0pt, minimum size=1.5mm}]

\node[roundnode,label=right:{$u^{}_1$}] at (1,0) (u1) {};
\node[roundnode,label=above right:{$u^{}_2$}] at (0.78539816339,0.70710678118) (u2) {};
\node[roundnode,label=:{$u^{}_3$}] at (0,1) (u3) {};
\node[roundnode,label=above left:{$u^{}_4$}] at (-0.78539816339,0.70710678118) (u4) {};
\node[roundnode,label=left:{$u^{}_5$}] at (-1,0) (u5) {};
\node[roundnode,label=left:{$u^{}_6$}] at (-0.78539816339,-0.70710678118) (u6) {};
\node[roundnode,label=below:{$u^{}_7$}] at (0,-1) (u7) {};
\node[roundnode,label=below right:{$u^{}_n$}] at (0.78539816339,-0.70710678118) (un) {};

\draw[-] (un) -- (u1) -- (u2) -- (u3) -- (u4) -- (u5) -- (u6) -- (u7);

\foreach \i in {0.25,0.5,0.75}
\fill ($(un)!\i!(u7)$) circle[radius=1pt];

\end{tikzpicture}
\end{document}

Drawing dotted lines is one way to produce this picture. (mentioned is comments by Andrew Swann also.). IS this okay for you?

\documentclass[12pt]{article}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}[roundnode/.style={circle, fill=black!70, inner sep=0pt, minimum size=1.5mm}]

\node[roundnode,label=right:{$u^{}_1$}] at (1,0) (u1) {};
\node[roundnode,label=above right:{$u^{}_2$}] at (0.78539816339,0.70710678118) (u2) {};
\node[roundnode,label=:{$u^{}_3$}] at (0,1) (u3) {};
\node[roundnode,label=above left:{$u^{}_4$}] at (-0.78539816339,0.70710678118) (u4) {};
\node[roundnode,label=left:{$u^{}_5$}] at (-1,0) (u5) {};
\node[roundnode,label=left:{$u^{}_6$}] at (-0.78539816339,-0.70710678118) (u6) {};
\node[roundnode,label=below:{$u^{}_7$}] at (0,-1) (u7) {};
\node[roundnode,label=below right:{$u^{}_n$}] at (0.78539816339,-0.70710678118) (un) {};

\draw[-] (un) -- (u1) -- (u2) -- (u3) -- (u4) -- (u5) -- (u6) -- (u7);
\draw[loosely dotted,thick] (un)--(u7);
\end{tikzpicture}
\end{document}