let f be FinSequence of (TOP-REAL 2); for p being Point of (TOP-REAL 2) st p in L~ f & len (R_Cut f,p) >= 2 holds
f . 1 in L~ (R_Cut f,p)
let p be Point of (TOP-REAL 2); ( p in L~ f & len (R_Cut f,p) >= 2 implies f . 1 in L~ (R_Cut f,p) )
assume A1:
p in L~ f
; ( not len (R_Cut f,p) >= 2 or f . 1 in L~ (R_Cut f,p) )
then
len f <> 0
by TOPREAL1:28;
then
len f > 0
by NAT_1:3;
then
0 + 1 <= len f
by NAT_1:13;
then A2:
(R_Cut f,p) . 1 = f . 1
by A1, JORDAN1B:4;
assume
2 <= len (R_Cut f,p)
; f . 1 in L~ (R_Cut f,p)
hence
f . 1 in L~ (R_Cut f,p)
by A2, JORDAN3:34; verum