let f be FinSequence of (TOP-REAL 2); for p being Point of (TOP-REAL 2) st p in L~ f & f is weakly-one-to-one holds
B_Cut f,p,p = <*p*>
let p be Point of (TOP-REAL 2); ( p in L~ f & f is weakly-one-to-one implies B_Cut f,p,p = <*p*> )
assume that
A1:
p in L~ f
and
A2:
f is weakly-one-to-one
; B_Cut f,p,p = <*p*>
A3:
1 <= Index p,f
by A1, JORDAN3:41;
(L_Cut f,p) . 1 = p
by A1, JORDAN3:58;
then A4:
R_Cut (L_Cut f,p),p = <*p*>
by JORDAN3:def 5;
A5:
Index p,f < len f
by A1, JORDAN3:41;
then A6:
(Index p,f) + 1 <= len f
by NAT_1:13;
then A7:
(Index p,f) + 1 in dom f
by A3, SEQ_4:151;
f . (Index p,f) <> f . ((Index p,f) + 1)
by A2, A5, A3, Def2;
then A8:
f . (Index p,f) <> f /. ((Index p,f) + 1)
by A7, PARTFUN1:def 8;
Index p,f in dom f
by A3, A6, SEQ_4:151;
then A9:
f /. (Index p,f) <> f /. ((Index p,f) + 1)
by A8, PARTFUN1:def 8;
p in LSeg f,(Index p,f)
by A1, JORDAN3:42;
then
p in LSeg (f /. (Index p,f)),(f /. ((Index p,f) + 1))
by A3, A6, TOPREAL1:def 5;
then
LE p,p,f /. (Index p,f),f /. ((Index p,f) + 1)
by A9, JORDAN5B:9;
hence
B_Cut f,p,p = <*p*>
by A4, JORDAN3:def 8; verum