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

% Ex. No. 68 (Section 10.1.9 : Option \tkzname{orthogonal normed} and $K=2$)

\begin{tikzpicture}[scale=1.2,
   vect/.style={->,shorten >=3pt,>=latex'}]
   \tkzDefPoint(2,3){A}   \tkzDefPoint(5,1){B}
   \tkzDefPointWith[orthogonal normed,K=2](A,B)
   \tkzGetPoint{C}
   \tkzDrawPoints[color=red](A,B,C)
   \tkzDrawCircle[R](A,2cm)
   \tkzDrawSegments[vect](A,B A,C)
   \tkzMarkRightAngle[fill=gray!20](B,A,C)
   \tkzLabelPoints[above=3pt](A,B,C)
\end{tikzpicture}

\end{document}