defpred S1[ Element of REAL , Element of REAL , set ] means ex c being Element of REAL 2 st
( c = $3 & $3 = <*$1,$2*> );
A1:
for x, y being Element of REAL ex u being Element of REAL 2 st S1[x,y,u]
proof
let x,
y be
Element of
REAL ;
:: thesis: ex u being Element of REAL 2 st S1[x,y,u]
take
<*x,y*>
;
:: thesis: ( <*x,y*> is Element of REAL 2 & S1[x,y,<*x,y*>] )
A2:
<*x,y*> in 2
-tuples_on REAL
by CATALG_1:10;
thus
<*x,y*> is
Element of
REAL 2
by CATALG_1:10;
:: thesis: S1[x,y,<*x,y*>]
thus
S1[
x,
y,
<*x,y*>]
by A2;
:: thesis: verum
end;
consider f being Function of [:REAL ,REAL :],(REAL 2) such that
A3:
for x, y being Element of REAL holds S1[x,y,f . x,y]
from BINOP_1:sch 3(A1);
( the carrier of [:R^1 ,R^1 :] = [:the carrier of R^1 ,the carrier of R^1 :] & the carrier of R^1 = REAL & the carrier of (TOP-REAL 2) = REAL 2 )
by BORSUK_1:def 5, EUCLID:25, TOPMETR:24;
then reconsider f = f as Function of [:R^1 ,R^1 :],(TOP-REAL 2) ;
take
f
; :: according to T_0TOPSP:def 1 :: thesis: f is being_homeomorphism
for x, y being Real holds f . [x,y] = <*x,y*>
hence
f is being_homeomorphism
by Th85; :: thesis: verum