\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,scale=1.3]
    \newcommand{\radius}{5}
    \newcommand{\TriangleAngle}{30}
    \tkzDefPoint(0,0){A}
    \tkzDefPoint(\radius,0){B}
    \tkzDefPoint(\TriangleAngle:{cos(\TriangleAngle*\FPpi/180)*\radius}){C}
    \tkzDefPoint({cos(\TriangleAngle*\FPpi/180)*\radius*cos(\TriangleAngle*\FPpi/180)},0){E}

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

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

    % Label lines
    \tkzLabelSegment[right](B,C){$a$}
    \tkzLabelSegment[above left=-0.1](A,C){$b$}
    \tkzLabelSegment[below](A,B){$c$}
    \tkzLabelSegment[above=-0.1](A,E){$q$}
    \tkzLabelSegment[above=-0.1](E,B){$p$}

    % Mark angles
    % \tkzMarkAngle[arc=l,size=0.6cm,fill=green!30](B,A,C)
    % \tkzLabelAngle[pos=0.3](B,A,C){$\alpha$}

    % \tkzMarkAngle[arc=l,size=0.6cm,fill=green!30](C,B,A)
    % \tkzLabelAngle[pos=0.45](C,B,A){$\beta$}

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

    \draw[thin] pic[draw, angle radius=4mm,"$\cdot$",angle eccentricity=.5]{angle=B--E--C};
    \draw[thin] pic[draw, angle radius=4mm,"$\cdot$",angle eccentricity=.5]{angle=A--C--B};

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