\documentclass[margin=6pt]{standalone}
\usepackage{tkz-euclide}
\usepackage{tkz-elements}
\begin{document}
\begin{tkzelements}
scale = 2
z.A = point: new(0,0)
z.B = point: new(4,0)
z.C = point: new(0,3)
T.ABC = triangle: new (z.A,z.B,z.C)
p = T.ABC.a + T.ABC.b + T.ABC.c
SA = math.deg(T.ABC.alpha + T.ABC.beta + T.ABC.gamma)
alpha = T.ABC.alpha
\end{tkzelements}
\begin{tikzpicture}
\tkzGetNodes
\pgfkeys{/pgf/number format/.cd,std,precision=5}
\tkzDrawPolygons(A,B,C)
\tkzLabelPoints(A,B)
\tkzLabelPoints[above](C)
\tkzText[right](0,-1){Le périmètre est \pgfmathprintnumber{\tkzUseLua{p}} cm}
\tkzText[right](0,-3){L'angle en $A$ vaut \pgfmathprintnumber{\tkzUseLua{alpha}} rad}
\pgfkeys{/pgf/number format/.cd,std,precision=0}
\tkzText[right](0,-2){La somme des angles est $\pgfmathprintnumber{\tkzUseLua{SA}}^\circ$}
\end{tikzpicture}
\end{document}
