let p be Point of (TOP-REAL 2); :: thesis: for C being compact Subset of (TOP-REAL 2) st p in BDD C holds
p `2 <> S-bound (BDD C)
let C be compact Subset of (TOP-REAL 2); :: thesis: ( p in BDD C implies p `2 <> S-bound (BDD C) )
assume A1:
p in BDD C
; :: thesis: p `2 <> S-bound (BDD C)
reconsider P = p as Point of (Euclid 2) by Lm3;
consider r being Real such that
A2:
( r > 0 & Ball P,r c= BDD C )
by A1, Th29;
assume A3:
p `2 = S-bound (BDD C)
; :: thesis: contradiction
A4:
BDD C is Bounded
by JORDAN2C:114;
A5:
0 < r / 2
by A2, XREAL_1:141;
A6:
r / 2 < r
by A2, XREAL_1:218;
(p `2 ) + (r / 2) > (p `2 ) + 0
by A5, XREAL_1:8;
then A7:
(p `2 ) - (r / 2) < p `2
by XREAL_1:21;
set EX = |[(p `1 ),((p `2 ) - (r / 2))]|;
P = |[(p `1 ),(p `2 )]|
by EUCLID:57;
then A8:
|[(p `1 ),((p `2 ) - (r / 2))]| in Ball P,r
by A2, A6, GOBOARD6:13;
not |[(p `1 ),((p `2 ) - (r / 2))]| in BDD C
hence
contradiction
by A2, A8; :: thesis: verum