thus
IAA /\ ICC c= {[(1 / 2),0]}
XBOOLE_0:def 10 {[(1 / 2),0]} c= IAA /\ ICCproof
let x be
object ;
TARSKI:def 3 ( not x in IAA /\ ICC or x in {[(1 / 2),0]} )
assume A1:
x in IAA /\ ICC
;
x in {[(1 / 2),0]}
then reconsider y =
x as
Point of
[:I[01],I[01]:] ;
x in IAA
by A1, XBOOLE_0:def 4;
then A2:
y `1 <= 1
/ 2
by Th59;
A3:
x in ICC
by A1, XBOOLE_0:def 4;
then
y `1 >= 1
/ 2
by Th60;
then A4:
y `1 = 1
/ 2
by A2, XXREAL_0:1;
y in the
carrier of
[:I[01],I[01]:]
;
then A5:
y in [: the carrier of I[01], the carrier of I[01]:]
by BORSUK_1:def 2;
A6:
y `2 is
Point of
I[01]
by Th27;
ex
q being
Point of
[:I[01],I[01]:] st
(
q = y &
q `2 <= (2 * (q `1)) - 1 )
by A3, Th55;
then
y `2 = 0
by A4, A6, BORSUK_1:43;
then
y = [(1 / 2),0]
by A5, A4, MCART_1:21;
hence
x in {[(1 / 2),0]}
by TARSKI:def 1;
verum
end;
1 / 2 is Point of I[01]
by BORSUK_1:43;
then
( [(1 / 2),0] in IAA & [(1 / 2),0] in ICC )
by Th69, Th70;
then
[(1 / 2),0] in IAA /\ ICC
by XBOOLE_0:def 4;
hence
{[(1 / 2),0]} c= IAA /\ ICC
by ZFMISC_1:31; verum