291 \end{tikzpicture} 

   291 \end{tikzpicture} \\

   292 \begin{tikzpicture}[baseline]

   293 \begin{scope}

   294 \clip (-1.3,-2) rectangle (0,2);

   295 \node[draw] (c) at (0,0) [ellipse, minimum height=2cm,minimum width=2.5cm] {};

   296 \end{scope}

   297 \begin{scope}

   298 \clip (1,-2) rectangle (0,2);

   299 \node[draw] (d) at (0,-0.4) [ellipse, minimum height=1.2cm, minimum width=1.5cm] {};

   300 \end{scope}

   301 \draw (c.north) -- (d.north);

   302 \draw[dashed] (d.north) -- (d.south);

   303 \node[right=8,below=4] at (c) {$g$};

   304 \node[left=10] at (c) {$f$};

   305 \end{tikzpicture} & =

   306 \begin{tikzpicture}[baseline]

   307 \begin{scope}

   308 	\clip (-1.3,-2) rectangle (0,2);

   309 	\node[draw] (c) at (0,0) [ellipse, minimum height=2cm,minimum width=2.5cm] {};

   310 \end{scope}

   311 \draw[dashed] (c.north) to[out=-120,in=120] (c.south);

   312 \draw[dashed] (c.south) to[out=60,in=-90] (0.35,0) node (m) {};

   313 \draw (m.center) to[out=90,in=-60] (c.north);

   314 \begin{scope}

   315 	\clip (c.north) to[out=-120,in=120] (c.south) to[out=60,in=-90] (m) to[out=90,in=-60] (c.north);

   316 	\foreach \y in {1,0.86,...,-1} {

   317 		\draw[green!50!brown] (-1,\y)--(1,\y);

   318 	}

   319 \end{scope}

   320 \draw (m.center) .. controls +(1,0) and +(1,0) .. (c.south);

   321 \node[right=15,below=8] at (c) {$g$};

   322 \node[left=12] at (c) {$f$};

   323 \end{tikzpicture}