\begin{pspicture}(-0.5,-0.8)(4.2,4)
%%%%%%%%%%%%%%%%%%%%Koordinaten
\psaxes[Ox=0,Dx=1,Oy=0,Dy=1,linewidth=0.1pt]{->}(0,0)(-0.2,-0.2)(3.5,3.5)%Schnittpunkt, x0, y0   x1,y1
%\psgrid(0,0)(4,4)
\rput[c](3.8,0){$x$} 
\rput[c](0,3.8){$y$} 


%%%%%%%%%%%%%%%%%%%%%%%Vektor%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\psline[linecolor=blue, linewidth=0.5pt]{->}(0,0)(1,3)


\psline[linecolor=red, linewidth=0.5pt]{->}(0,0)(3,1)


\psarc(0,0){2.5cm}{19}{71}
\rput[l](0.35, 0.75){$\alpha\left(\vec{a}, \vec{b}\right)$}



\rput[l](3.2, 1){\color{red}$\vec{a}$}

\rput[l](1, 3.2){\color{blue}$\vec{b}$}
\end{pspicture}