\def\xstrut{\vphantom{\frac{(A)^1}{(B)^1}}}


\begin{pspicture}(-0.5,-0.5)(7,4)

\rput[l](0.5,3.6){$\xstrut \bullet$\hspace{7mm}Die Menge hei{\ss}t $\xstrut \IR^3$ / $\IR^n$;}
\rput[l](0.5,3.0){$\xstrut \bullet$\hspace{7mm}Dabei ist $ \xstrut n$ eine nat\"{u}rliche Zahl, $\xstrut n\in\IN$.}
\rput[l](0.5,2.4){$\xstrut \bullet$\hspace{7mm}Also:  $\xstrut  \IR^3  = \left\{ {\left( {a_1 ,a_2 ,a_3 } \right)|a_1,a_2 ,a_3\in \left. \IR \right\}} \right.$}
\rput[l](0.5,1.8){$\bullet$\hspace{7mm}$\IR^3=\left\{\rnode[t]{ae}{\psframebox*[fillcolor=darkyellow, linestyle=none]{ \left(a_1 , \ldots,a_n\right)}}|a_1 , \ldots a_n  \in \IR\right\}$}
\rput[l](1,1.2){\rnode{a}{n-Tupel}}%
\nccurve[angleB=-90]{->}{a}{ae}


% \IR^3 = \left\{ {\psframebox*[fillcolor=darkyellow,  linestyle=none]{{\left( {a_1 , \ldots \rnode[t]{ae},a_n } \right)}}}
%{|a_1 , \ldots a_n  \in \IR} \right\}


\end{pspicture}