\documentclass[a4paper,12pt]{report}
\usepackage{german,pstricks,pst-node,pst-tree}
\usepackage[latin1]{inputenc}
\begin{document}

\psset{unit=1cm}
\hbox{
\pspicture(0,0)(8,5)
  \rput(1,2){\rnode{A}{Gleichung}}
  \rput(4,0.5){\ovalnode{B}{sichtbar}}
  \rput(6,3){\rnode{C}{Kreis}}
  \rput(7,4.5){\rnode{D}{$x^2+y^2=r^2$}}
  \ncline{->}{A}{D}
  \ncarc{->}{C}{D} \Bput{\footnotesize Beziehung}
  \ncarc{->}{D}{C}
  \nccurve[angleA=240, angleB=90,linestyle=dotted]
    {->}{C}{B}
\endpspicture\hfil
\pstree[treemode=R,levelsep=1cm,radius=2pt]
  {\Tcircle{root}}
  { \pstree{\TC*}{ \Tr{A}  \Tr{B}  \Tr{C} }
    \pstree{\TC*}
      { \pstree{\TC*}{\Tr{$A_1$}  \Tr{$A_2$}}
        \pstree{\TC*}{\Tr{$B_1$}  \Tr{$B_2$}}
      }
    \pstree[treemode=D]{\TC}
      {\TR{$x^2$}  \TR{$y_a^2$}  \TR{$\frac{1}{x+y}$}
      }
  }
}

\end{document}