let V be non empty set ; for W being non empty Subset of V holds Ens W is full Subcategory of Ens V
let W be non empty Subset of V; Ens W is full Subcategory of Ens V
reconsider E = Ens W as Subcategory of Ens V by Lm7;
for a, b being Object of E
for a9, b9 being Object of (Ens V) st a = a9 & b = b9 holds
Hom (a,b) = Hom (a9,b9)
proof
let a,
b be
Object of
E;
for a9, b9 being Object of (Ens V) st a = a9 & b = b9 holds
Hom (a,b) = Hom (a9,b9)let a9,
b9 be
Object of
(Ens V);
( a = a9 & b = b9 implies Hom (a,b) = Hom (a9,b9) )
assume A1:
(
a = a9 &
b = b9 )
;
Hom (a,b) = Hom (a9,b9)
reconsider aa =
a,
bb =
b as
Element of
(Ens W) ;
(
Hom (
aa,
bb)
= Maps (
(@ aa),
(@ bb)) &
Hom (
a9,
b9)
= Maps (
(@ a9),
(@ b9)) )
by Th26;
hence
Hom (
a,
b)
= Hom (
a9,
b9)
by A1, Lm5;
verum
end;
hence
Ens W is full Subcategory of Ens V
by CAT_2:def 6; verum