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

% Ex. No. 245 (Section 31.1.3 : Example 3: extend lines)

\begin{tikzpicture}
  \tkzSetUpLine[add=.5 and .5]
  \tkzDefPoints{0/0/A,4/0/B,1/3/C}
  \tkzDrawLines(A,B B,C A,C)
\end{tikzpicture}

\end{document}