let S be locally_directed OrderSortedSign; for X being V5() ManySortedSet of
for R being OSCongruence of S
for t being Element of TS (DTConOSA X) holds t in OSClass R,t
let X be V5() ManySortedSet of ; for R being OSCongruence of S
for t being Element of TS (DTConOSA X) holds t in OSClass R,t
let R be OSCongruence of S; for t being Element of TS (DTConOSA X) holds t in OSClass R,t
let t be Element of TS (DTConOSA X); t in OSClass R,t
set PTA = ParsedTermsOSA X;
reconsider x = t as Element of the Sorts of (ParsedTermsOSA X) . (LeastSort t) by Def12;
OSClass R,t =
OSClass R,x
by Def28
.=
Class (CompClass R,(CComp (LeastSort t))),x
;
hence
t in OSClass R,t
by EQREL_1:28, OSALG_4:6; verum