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$\forall$\=$A$, $C$:Type, $B$:($A$$\rightarrow$Type), ${\it eqa}$:EqDecider($A$), ${\it eqc}$:EqDecider($C$), $r$:($A$$\rightarrow$$C$), $f$:$a$:$A$ fp$\rightarrow$ $B$($a$),\+
\\[0ex]$c$:$C$.
\-\\[0ex]$c$ $\in$ dom(rename($r$;$f$)) $\Leftrightarrow$ ($\exists$$a$:$A$. $a$ $\in$ dom($f$) \& $c$ $=$ $r$($a$))
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