\input{preamble-standalone.ltx}
\begin{document}

% Ex. No. 56 (Section  8.2 : Placing a label with the library \tkzname{quotes})

\begin{tikzpicture}[trim left=-1cm]
 \tkzDefPoint["-60:$A_n$" ](2,3){A}
 \tkzDefPoint[shift={(2,3)},%
    "$B_n$" above left](31:3){B}
 \tkzDefPoint[shift={(2,3)},%
     "$C_n$" above right](158:3){C}
 \tkzDrawSegments[color=red,%
          line width=1pt](A,B A,C)
 \tkzDrawPoints[color=red](A,B,C)
\end{tikzpicture}

\end{document}