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

% Ex. No. 93 (Section 13.1.5 : Altitudes in a triangle)

\begin{tikzpicture}[scale=1.25]
 \tkzDefPoint(0,0){A} \tkzDefPoint(4,0){B}
 \tkzDefPoint(1,3){C} \tkzDrawPolygon(A,B,C)
 \tkzSetUpLine[color=magenta]
 \tkzDrawLine[altitude](B,C,A)
 \tkzDrawLine[altitude](C,A,B)
 \tkzDrawLine[altitude](A,B,C)
\end{tikzpicture}

\end{document}