\documentclass{article}
\usepackage[pdftex,active,tightpage]{preview}
\setlength\PreviewBorder{2mm}
\usepackage{tikz}
\usepackage{tkz-euclide}
\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]
    % \tkzInit[xmin=-1,xmax=2,ymin=-1,ymax=2] \tkzGrid

    \tkzDefPoint(0,0){A}
    \tkzDefPoint(3,0){B}
    \tkzDefPoint(0,3){C}

    % \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)

    % Mark angles
    \tkzMarkAngle[arc=l,size=0.3cm,fill=green!30](B,A,C)
    \tkzLabelAngle[pos=0.15](B,A,C){$\cdot$}

    \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=red!30](A,C,B)
    % \tkzLabelAngle[pos=0.4](A,C,B){$\gamma$}

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

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

    \node at (-0.2,-0.2) (AText) {\tiny $(0,0)$};
    \node at (3,-0.2) (BText) {\tiny $(1,0)$};
    \node at (0,3.2) (CText) {\tiny $(0,1)$};

    \tkzDrawPoints[size=1](A,B,C)
\end{tikzpicture}
\end{preview}
\end{document}
