Update 03_metric_spaces.tex

Fixed Typo

ib/antop/03_metric_spaces.tex

@@ -3,7 +3,7 @@ \subsection{Definition}
 	Let \( M \) be a set.
 	Then a \textit{metric} on \( M \) is a function \( d \colon M \times M \to \mathbb R \) such that
 	\begin{enumerate}
-		\item (positivity) \( \forall x,y \in M, d(x,y) \geq 0 \), and in particular, \( x = y \iff d(x,x) = 0 \)
+		\item (positivity) \( \forall x,y \in M, d(x,y) \geq 0 \), and in particular, \( x = y \iff d(x,y) = 0 \)
 		\item (symmetric) \( \forall x,y \in M, d(x,y) = d(y,x) \)
 		\item (triangle inequality) \( \forall x,y,z \in M, d(x,z) \leq d(x,y) + d(y,z) \).
 	\end{enumerate}