\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)(3,3)
\rput[c](1.5,2){\color{blue}$\vec{a}$}


%%%%%%%%%%%%%%%%%%%%%%%%%%Hilfslinien%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\psline[linecolor=blue,linewidth=0.1pt,linestyle=dashed](3,0)(3,3)
\psline[linecolor=blue,linewidth=0.1pt,linestyle=dashed](0,3)(3,3)
\rput[c](1.5,-0.6){\color{red}$a_1$}
\rput[c](3.7,1.5){\color{magenta}$a_2$}

%%%%%%%%%%%%%%%%%%%%%%Klammer unten)%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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\pscurve[linecolor=red]{-}(1.5,-0.4)(1.6,-0.23)(2, -0.15)(2.5,-0.15)(2.8,-0.15)(2.9, -0.1)(3,0)

%%%%%%%%%%%%%%%%%%%%%%Klammer rechts %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\pscurve[linecolor=magenta]{-}(3,0)(3.1, 0.1)(3.15, 0.2)(3.15, 0.5)(3.15,1)(3.23, 1.4)(3.4, 1.5)
\pscurve[linecolor=magenta]{-}(3.4, 1.5)(3.23, 1.6)(3.15, 2)(3.15, 2.5)(3.15, 2.8)(3.1, 2.9)(3,3)

\psdots(2.75,0.25)
\psarc[linecolor=blue]{->}(3,3){2cm}{165}{225}
\rput[l](0.5,3.6){\color{blue}\footnotesize{Länge $\sqrt{a^{2}_{1}+a^{2}_{2}}$ nach Pythagoras}}
\end{pspicture}