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

% Ex. No. 40 (Section  6.1.5 : Option \tkzname{ex})

\begin{tikzpicture}[scale=.5]
    \tkzDefPoints{0/1/A,3/2/B,1/4/C}
    \tkzDefTriangleCenter[ex](B,C,A)
    \tkzGetPoint{J_c}
    \tkzDefPointBy[projection=onto A--B](J_c)
    \tkzGetPoint{Tc}
    %or
    % \tkzDefCircle[ex](B,C,A)
    % \tkzGetFirstPoint{J_c}
    % \tkzGetSecondPoint{Tc}
    \tkzDrawPolygon[color=blue](A,B,C)
    \tkzDrawPoints(A,B,C,J_c)
    \tkzDrawCircle[red](J_c,Tc)
    \tkzDrawLines[add=1.5 and 0](A,C B,C)
    \tkzLabelPoints(J_c)
\end{tikzpicture}

\end{document}