\input{preamble-standalone.ltx} \begin{document} % Ex. No. 229 (Section 30.1.4 : Triangle altitudes) \begin{tikzpicture}[scale=.8] \tkzDefPoint(0,0){C} \tkzDefPoint(7,0){B} \tkzDefPoint(5,6){A} \tkzDrawPolygon(A,B,C) \tkzDefMidPoint(C,B) \tkzGetPoint{I} \tkzDrawArc(I,B)(C) \tkzInterLC(A,C)(I,B) \tkzGetSecondPoint{B'} \tkzInterLC(A,B)(I,B) \tkzGetFirstPoint{C'} \tkzInterLL(B,B')(C,C') \tkzGetPoint{H} \tkzInterLL(A,H)(C,B) \tkzGetPoint{A'} \tkzDefCircle[circum](A,B',C') \tkzGetPoint{O} \tkzDrawCircle[color=red](O,A) \tkzDrawSegments[color=orange](B,B' C,C' A,A') \tkzMarkRightAngles(C,B',B B,C',C C,A',A) \tkzDrawPoints(A,B,C,A',B',C',H) \tkzLabelPoints(A,B,C,A',B',C',H) \end{tikzpicture} \end{document}