\documentclass[dvipdfmx,margin=1mm]{standalone}
\usepackage{tikz}
\usetikzlibrary{shapes.geometric}
\begin{document}
\begin{tikzpicture}[
foo/.style={inner sep=0,minimum size=0.6mm,fill=black,circle},
bar/.style={draw,shape=isosceles triangle,anchor=apex,shape border rotate=90,minimum width=0.6cm,minimum height=1cm},
]
\node [foo,label=above:$\alpha$] (a) at (0,2) {};
\node [foo,label=above:$\beta$] (b) at (1,1) {};
\node [foo,label=above:$\gamma$] (c) at (-1,1) {};
\node [bar] at (0,2) {};
\node [bar] at (1,1) {};
\node [bar] at (-1,1) {};
\draw (a) -- (b);
\draw (a) -- (c);
\end{tikzpicture}
\end{document}
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