% Dans le préambule
% -----------------
\usepackage{tikz}
% -----------------

\begin{tikzpicture}
\draw(1,1) node{$\bullet$} node[left]{$A$};
\draw(1,0) node{$\bullet$} node[right]{$B$};
\draw(3,1) node{$\bullet$} node[below right]{$\Delta$};
\draw(3,0) node{$\bullet$} node[right, rotate=30]{$M_1$};
\end{tikzpicture}