let f be FinSequence of (TOP-REAL 2); :: thesis: ( f is special implies for p being Point of (TOP-REAL 2) st p in L~ f holds
L_Cut f,p is special )
assume A1: f is special ; :: thesis: for p being Point of (TOP-REAL 2) st p in L~ f holds
L_Cut f,p is special
let p be Point of (TOP-REAL 2); :: thesis: ( p in L~ f implies L_Cut f,p is special )
A2: mid f,((Index p,f) + 1),(len f) is special by A1, Th27;
A3: <*p*> /. 1 = p by FINSEQ_4:25;
assume A4: p in L~ f ; :: thesis: L_Cut f,p is special
then Index p,f < len f by JORDAN3:41;
then A5: (Index p,f) + 1 <= len f by NAT_1:13;
1 <= Index p,f by A4, JORDAN3:41;
then A6: LSeg f,(Index p,f) = LSeg (f /. (Index p,f)),(f /. ((Index p,f) + 1)) by A5, TOPREAL1:def 5;
A7: now
per cases ( LSeg f,(Index p,f) is vertical or LSeg f,(Index p,f) is horizontal ) by A1, SPPOL_1:41;
case LSeg f,(Index p,f) is vertical ; :: thesis: p `1 = (f /. ((Index p,f) + 1)) `1
hence p `1 = (f /. ((Index p,f) + 1)) `1 by A4, A6, JORDAN5B:32, SPPOL_1:64; :: thesis: verum
end;
case LSeg f,(Index p,f) is horizontal ; :: thesis: p `2 = (f /. ((Index p,f) + 1)) `2
hence p `2 = (f /. ((Index p,f) + 1)) `2 by A4, A6, JORDAN5B:32, SPPOL_1:63; :: thesis: verum
end;
end;
end;
A8: len <*p*> = 1 by FINSEQ_1:56;
len f <> 0 by A4, TOPREAL1:28;
then len f > 0 by NAT_1:3;
then len f >= 0 + 1 by NAT_1:13;
then A9: len f in dom f by FINSEQ_3:27;
(Index p,f) + 1 >= 1 by NAT_1:11;
then (Index p,f) + 1 in dom f by A5, FINSEQ_3:27;
then A10: (mid f,((Index p,f) + 1),(len f)) /. 1 = f /. ((Index p,f) + 1) by A9, SPRECT_2:12;
A11: <*p*> is special by SPPOL_2:39;
per cases ( p <> f . ((Index p,f) + 1) or p = f . ((Index p,f) + 1) ) ;
suppose p <> f . ((Index p,f) + 1) ; :: thesis: L_Cut f,p is special
then L_Cut f,p = <*p*> ^ (mid f,((Index p,f) + 1),(len f)) by JORDAN3:def 4;
hence L_Cut f,p is special by A11, A2, A8, A3, A10, A7, GOBOARD2:13; :: thesis: verum
end;
suppose p = f . ((Index p,f) + 1) ; :: thesis: L_Cut f,p is special
hence L_Cut f,p is special by A2, JORDAN3:def 4; :: thesis: verum
end;
end;