set f = LocSeq M,S;
set C = canonical_isomorphism_of (RelIncl (order_type_of (RelIncl M))),(RelIncl M);
let x1, x2 be set ; FUNCT_1:def 8 ( not x1 in proj1 (LocSeq M,S) or not x2 in proj1 (LocSeq M,S) or not (LocSeq M,S) . x1 = (LocSeq M,S) . x2 or x1 = x2 )
assume that
A1:
( x1 in dom (LocSeq M,S) & x2 in dom (LocSeq M,S) )
and
A2:
(LocSeq M,S) . x1 = (LocSeq M,S) . x2
; x1 = x2
A3:
dom (LocSeq M,S) = card M
by Def4;
then B4:
( (LocSeq M,S) . x1 = (canonical_isomorphism_of (RelIncl (order_type_of (RelIncl M))),(RelIncl M)) . x1 & (LocSeq M,S) . x2 = (canonical_isomorphism_of (RelIncl (order_type_of (RelIncl M))),(RelIncl M)) . x2 )
by A1, Def4;
A5:
card M c= order_type_of (RelIncl M)
by CARD_5:51;
consider phi being Ordinal-Sequence such that
A6:
phi = canonical_isomorphism_of (RelIncl (order_type_of (RelIncl M))),(RelIncl M)
and
A7:
phi is increasing
and
A8:
dom phi = order_type_of (RelIncl M)
and
rng phi = M
by CARD_5:14;
phi is one-to-one
by A7, CARD_5:20;
hence
x1 = x2
by A1, A2, A3, B4, A6, A8, A5, FUNCT_1:def 8; verum