LaTeX-examples/tikz/parallelogram-triangle-area/parallelogram-triangle-area.tex

\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(0,0){A}
    \tkzDefPoint(4,0){B}
    \tkzDefPoint(5,3){C}
    \tkzDefPoint(1,3){D}
    \tkzDefPoint(1,0){E}

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

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

    % \tkzMarkAngle[arc=l,size=0.6cm,fill=red!30](C,B,A)
    % \tkzLabelAngle[pos=0.4](C,B,A){$\beta$}

    % \tkzMarkAngle[arc=l,size=0.6cm,fill=blue!30](A,C,B)
    % \tkzLabelAngle[pos=0.4](A,C,B){$\gamma$}

    % Label lines
    \tkzLabelSegment[below](A,B){$a$}
    \tkzLabelSegment[left](A,D){$b$}
    % \tkzLabelSegment[right](B,C){$a$}

    % Draw polygon
    \tkzDrawPolygon[fill=blue!30](A,B,D)

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

    % Draw polygon
    \tkzDrawPolygon[thick](A,B,C,D)

    \tkzDrawSegment[dashed](D,E)
    \tkzLabelSegment[right](D,E){$h$}

    \draw[thin] pic[draw, angle radius=2mm,"$\cdot$",angle eccentricity=.5]{angle=B--E--D};
\end{tikzpicture}
\end{preview}
\end{document}