\documentclass{article}
\usepackage[pdftex,active,tightpage]{preview}
\setlength\PreviewBorder{2mm}
\usepackage{tikz}
\usepackage{tkz-euclide}
\usetikzlibrary{angles,quotes}

\usetkzobj{all}
\usetikzlibrary{shapes, calc, decorations}
\usepackage{amsmath,amssymb}
\usepackage{helvet}
\usepackage[eulergreek]{sansmath}

\begin{document}
\begin{preview}
\begin{tikzpicture}[very thick,font=\sansmath\sffamily]
    \tkzDefPoint(5,2){A}
    \tkzDefPoint(0,0){B}
    \tkzDefPoint(6.8,0){C}
    \tkzDefPoint(5,0){E}

    % \tkzLabelPoints[above,font=\sansmath\sffamily](A)
    % \tkzLabelPoints[below left,font=\sansmath\sffamily](B)
    % \tkzLabelPoints[below right,font=\sansmath\sffamily](C)

    % Draw polygon
    \tkzDrawPolygon[fill=gray!10](A,B,C)

    % Label line segments
    \tkzLabelSegment[below](B,C){$a$}
    \tkzLabelSegment[right](A,C){$b$}
    \tkzLabelSegment[above left](A,B){$c$}
    \tkzLabelSegment[above](B,E){$d$}
    \tkzLabelSegment[above](E,C){$e$}

    % Mark angles
    \tkzMarkAngle[arc=l,size=0.6cm,fill=green!30](A,C,B)
    \tkzLabelAngle[pos=0.42](A,C,B){$\gamma$}

    \tkzDrawSegment[dashed](A,E)
    \tkzLabelSegment[left](A,E){$h$}

    \draw[thin] pic[draw, angle radius=2mm,"$\cdot$",angle eccentricity=.5]{
        angle=C--E--A};

    % Draw polygon
    \tkzDrawPolygon(A,B,C)
\end{tikzpicture}
\end{preview}
\end{document}