\documentclass[border=1pt]{standalone}
\usepackage[polish]{babel}
\usepackage[utf8]{inputenc} 
\usepackage[T1]{fontenc}
\usepackage{fourier}
\usepackage{tikz}


\begin{document}

\begin{tikzpicture}
\coordinate (A) at (1,1);
\coordinate [label=above:{$B$}] (B) at (3,2);
\draw (A) -- (B) -- ++(1,-1) coordinate (C) -- cycle;
\draw (A) circle (1);
\draw (B) circle (1);
\draw (A) node [left] {$A$};
\draw (C) node [right] {$C$};
\end{tikzpicture}

\end{document}