$\forall$$A$:Type, ${\it eq}$:EqDecider($A$), $f$,$g$:fpf($A$; $a$.Type), $a$:$A$.
\\[0ex]subtype\_rel(fpf{-}cap(fpf{-}join(${\it eq}$; $f$; $g$); ${\it eq}$; $a$; top); fpf{-}cap($f$; ${\it eq}$; $a$; top))