\input{Figs/Klein.Base.tikz};

\draw
   [
      variable=\t,
      name path=Circle1,
      domain=\ThetaP:\ThetaQ,
   ]
   plot
   (
      { \R*cos(\t) },
      { \R*sin(\t) }
   );

\tikzfillbetween[of=Cord and Circle1]{gray, opacity=0.5};

\draw[thick] (O) circle(\R);

\draw[-Latex] (M) -- ++(N) node[right] {$\underline{n}$};
%\draw[-Latex] (M) -- ++(V);

\fill[name path=Circle,darkgray, opacity=0.1] (O) circle(\R);

\draw[very thin] (O) --(R);
\input{Figs/Klein.Cord.tikz};
