Fix typo

Author: ctafur80

content/sets-functions-relations/relations/relations-as-sets.tex

@@ -21,7 +21,7 @@
 pointing out that we can look at relations as a special sort of set. 
 
 For this, recall two things from \olref[sfr][set][pai]{sec}. First,
-recall the notion of a \emph{ordered pair}: given $a$ and $b$, we can
+recall the notion of an \emph{ordered pair}: given $a$ and $b$, we can
 form~$\tuple{a, b}$. Importantly, the order of elements \emph{does}
 matter here. So if $a \neq b$ then $\tuple{a, b} \neq \tuple{b, a}$.
 (Contrast this with unordered pairs, i.e., $2$-element sets, where