let M be non countable Aleph; ( M is strongly_inaccessible implies card (Rank M) = M )
consider L being Sequence such that
A1:
( dom L = M & ( for A being Ordinal st A in M holds
L . A = H1(A) ) )
from ORDINAL2:sch 2();
A2:
rng L is c=-linear
proof
let X,
Y be
set ;
ORDINAL1:def 8 ( not X in rng L or not Y in rng L or X,Y are_c=-comparable )
assume
X in rng L
;
( not Y in rng L or X,Y are_c=-comparable )
then consider x being
object such that A3:
x in dom L
and A4:
X = L . x
by FUNCT_1:def 3;
assume
Y in rng L
;
X,Y are_c=-comparable
then consider y being
object such that A5:
y in dom L
and A6:
Y = L . y
by FUNCT_1:def 3;
reconsider x =
x,
y =
y as
Ordinal by A3, A5;
A7:
Y = Rank y
by A1, A5, A6;
A8:
(
x c= y or
y c= x )
;
X = Rank x
by A1, A3, A4;
then
(
X c= Y or
Y c= X )
by A7, A8, CLASSES1:37;
hence
X,
Y are_c=-comparable
by XBOOLE_0:def 9;
verum
end;
card M c= card (Rank M)
by CARD_1:11, CLASSES1:38;
then A9:
M c= card (Rank M)
;
A10: Rank M =
Union L
by A1, CLASSES2:24
.=
union (rng L)
by CARD_3:def 4
;
assume A11:
M is strongly_inaccessible
; card (Rank M) = M
then
card (union (rng L)) c= M
by A2, CARD_3:46;
hence
card (Rank M) = M
by A10, A9, XBOOLE_0:def 10; verum