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

% Ex. No. 189 (Section 22.5 : Determining a slope)

\begin{tikzpicture}[scale=1.5]
  \tkzInit[xmax=4,ymax=5]\tkzGrid[sub]
  \tkzDefPoint(1,2){A}    \tkzDefPoint(3,4){B}
  \tkzDefPoint(3,2){C}    \tkzDefPoint(3,1){D}
  \tkzDrawSegments(A,B A,C A,D)
  \tkzDrawPoints[color=red](A,B,C,D)
  \tkzLabelPoints(A,B,C,D)
  \tkzFindSlope(A,B){SAB} \tkzFindSlope(A,C){SAC}
  \tkzFindSlope(A,D){SAD}
  \pgfkeys{/pgf/number format/.cd,fixed,precision=2}
  \tkzText[fill=Gold!50,draw=brown](1,4)%
  {The slope of (AB) is : $\pgfmathprintnumber{\SAB}$}
  \tkzText[fill=Gold!50,draw=brown](1,3.5)%
  {The slope of (AC) is : $\pgfmathprintnumber{\SAC}$}
  \tkzText[fill=Gold!50,draw=brown](1,3)%
  {The slope of (AD) is : $\pgfmathprintnumber{\SAD}$}
\end{tikzpicture}

\end{document}