\ANG{
\begin{minipage}[t]{9cm}
%Fl"acheninhalt und Umfang von Kreisen, Kreissektor; BIGTEX verwenden
Berechnen Sie den Fl"acheninhalt und den Umfang der punktierten Fl"ache in
Abh"angigkeit von r und $\pi$!\\
Hinweis: Das Dreieck $SM_1M_3$ ist ein besonderes Dreieck!
\end{minipage}
\hfill
\begin{minipage}[t]{5cm}
\makebox[0cm]{}\\
\beginpicture

\setcoordinatesystem units <1mm,1mm> point at 0 0
\setplotarea x from -25 to 25, y from -30 to 30
\unitlength1mm

\circulararc 360 degrees from 20 0 center at 0 0
\circulararc 180 degrees from 0 -20 center at 0 -10
\circulararc -60 degrees from 0 0 center at 0 20

\setlinear
\plot 0 20 0 -20 /

\put {$M_1$} [Bl] at -6 -3
\put {$M_2$} [Bl] at -7 -11
\put {$M_3$} [Bl] at -2 21
\put {S} [Bl] at -20.5 9
\put {$\bullet$} at 0 0
\put {$\bullet$} at 0 20
\put {$\bullet$} at 0 -10
\put {$\bullet$} at -17.3205 10

\betweenarrows {r} [l] <0.5mm,0pt> from 0 0 to 0 20


\setquadratic
\hshade -20 0 0 -15 8.66 13.2288 -10 10 17.3205 -5 8.66 19.3649 
        0 0 20 5 0 19.3649 10 0 17.3205 15 0 13.2288 20 0 0 /
\hshade 0 0 0 5 -13.2288 0 10 -17.3205 0 15 -13.2288 0 20 0 0 /
 
         
\endpicture
\end{minipage}
}
\LSG{
$A=\frac{17}{24} r^2 \pi - \frac{1}{4} \sqrt{3} r^2;
          U=\frac{13}{6} r \pi$
}