Fix wrong math ...

prerequisites.tex

@@ -22,7 +22,7 @@
 		\item $\so 4$ is isomorphic to the isometry group of $\S^3$.
 		\item Subgroups $\Gamma \leqslant \so 4$ define \textcolor{darkyellow}{equivalence classes} of orbits on $\S^3$ by the standard action of $\so 4$ on $\R^4$, i.e. $x \sim y$ iff $x = My$ for some $M \in \Gamma$.
 		      \pause
-		\item The obtain space is (\emph{sometimes}) a manifold. In particular, it is well defined and spherical for finite $\Gamma$.
+		\item The obtain space is (\emph{sometimes}) a manifold. In particular, the finite $\Gamma$ we will consider guarantee the manifold to be well defined and spherical.
 		\item This can be easily generalized to the $n$-sphere.
 	\end{itemize}
 \end{frame}