LaTeX Forum

\documentclass{scrbook}
\usepackage{tikz}
\usetikzlibrary{intersections}
\begin{document}
	\begin{tikzpicture}
	
	\draw[name path=links](0.5,0.5) -- (0.5,-3.5); % links
	\draw[name path=rechts](2.5,0.5) -- (2.5,-3.5); % rechts
	\draw[name path=kreisUnten](2.5,-3.5) arc (0:180:1); % Kreis Unten
	\draw[name path=kreisOben](2.5,0.5) arc (0:180:1); % Kreis Oben
	
\path [draw,line width=3,blue,name path=1and2,intersection segments={of=kreisOben and rechts,sequence={A1[reverse] -- B1[reverse]}}];
\path [draw,line width=3,blue,name path=3and4,intersection segments={of=links and kreisUnten,sequence={A1[reverse] -- B1[reverse]}}];
	
	\fill[red, name intersections={of= 1and2 and 3and4, name=foobar}];
	\end{tikzpicture}
\end{document}

\documentclass{scrbook}
\usepackage{tikz}
\begin{document}
\begin{tikzpicture}
    \path[fill=blue,draw=black]
        (.5,.5)
        -- (.5,-3.5)
        arc (180:0:1)
        -- (2.5,.5)
        arc (0:180:1)
    ;
\end{tikzpicture}
\end{document}