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diff --git a/library/relation.tex b/library/relation.tex
index b5aebcd..d63e747 100644
--- a/library/relation.tex
+++ b/library/relation.tex
@@ -422,6 +422,9 @@
\begin{proposition}\label{fld_cons}
$\fld{(\cons{(a,b)}{R})} = \cons{a}{\cons{b}{\fld{R}}}$.
\end{proposition}
+\begin{proof}
+ Follows by set extensionality.
+\end{proof}
\begin{proposition}\label{fld_union}
$\fld{(A\union B)} = \fld{A}\union\fld{B}$.
@@ -630,6 +633,7 @@ This lets us use the same symbol for composition of functions.
\begin{proof}
%$x\in\dom{R}$ and $z\in\ran{S}$.
There exists $y$ such that $x\mathrel{R} y\mathrel{S} z$ by \cref{circ,pair_eq_iff}.
+ Follows by assumption.
\end{proof}
\begin{proposition}\label{circ_iff}