Fix mistake

prerequisites.tex

@@ -19,7 +19,7 @@
 \begin{frame}{Quotients of the $3$-sphere}
 	\begin{itemize}
 		\item $\so 4$ is isomorphic to the isometry group of $\S^3$.
-		\item Subgroups $\Gamma \leqslant \so 4$ define equivalence classes of orbits on $\S^3$ by the standard action of $\so 4$ on $\R^3$, i.e. $x \sim y$ iff $x = My$ for some $M \in \Gamma$.
+		\item Subgroups $\Gamma \leqslant \so 4$ define 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 $M \in \Gamma$.
 		\item The obtain space is (\emph{sometimes}) a manifold. In particular, it is well defined and spherical for finite $\Gamma$.
 		\item This can be easily generalised to the $n$-sphere.
 	\end{itemize}