235   \begin{center}$\pi_1 + \pi_2 \alert{\not=} \pi_2 + \pi_1$\end{center}

   235   \begin{center}$\pi_1 + \pi_2 \alert{\not=} \pi_2 + \pi_1$\end{center}

   236   \end{minipage}};

   236   \end{minipage}};

   237   \end{tikzpicture}

   237   \end{tikzpicture}

   238   \end{textblock}}

   238   \end{textblock}}

   239 

   239 

   240   \end{frame}}

   242   \end{frame}}

   241   %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     

   243   %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%     

   242 *}

   244 *}

   243 

   245 

   244 text_raw {*

   246 text_raw {*