let f be FinSequence of (); :: thesis: for p, q being Point of () st f is being_S-Seq & p in L~ f & q in L~ f & p <> q & ( Index (p,f) < Index (q,f) or ( Index (p,f) = Index (q,f) & LE p,q,f /. (Index (p,f)),f /. ((Index (p,f)) + 1) ) ) holds
B_Cut (f,p,q) is_S-Seq_joining p,q

let p, q be Point of (); :: thesis: ( f is being_S-Seq & p in L~ f & q in L~ f & p <> q & ( Index (p,f) < Index (q,f) or ( Index (p,f) = Index (q,f) & LE p,q,f /. (Index (p,f)),f /. ((Index (p,f)) + 1) ) ) implies B_Cut (f,p,q) is_S-Seq_joining p,q )
assume that
A1: f is being_S-Seq and
A2: p in L~ f and
A3: q in L~ f and
A4: p <> q ; :: thesis: ( ( not Index (p,f) < Index (q,f) & not ( Index (p,f) = Index (q,f) & LE p,q,f /. (Index (p,f)),f /. ((Index (p,f)) + 1) ) ) or B_Cut (f,p,q) is_S-Seq_joining p,q )
assume A5: ( Index (p,f) < Index (q,f) or ( Index (p,f) = Index (q,f) & LE p,q,f /. (Index (p,f)),f /. ((Index (p,f)) + 1) ) ) ; :: thesis: B_Cut (f,p,q) is_S-Seq_joining p,q
then A6: B_Cut (f,p,q) = R_Cut ((L_Cut (f,p)),q) by A2, A3, Def7;
Index (p,f) < len f by ;
then A7: (Index (p,f)) + 1 <= len f by NAT_1:13;
A8: Index (q,f) < len f by ;
1 <= Index (q,f) by ;
then A9: 1 < len f by ;
A10: now :: thesis: ( ( Index (p,f) < Index (q,f) & not p = f . (len f) ) or ( Index (p,f) = Index (q,f) & LE p,q,f /. (Index (p,f)),f /. ((Index (p,f)) + 1) & not p = f . (len f) ) )
per cases ( Index (p,f) < Index (q,f) or ( Index (p,f) = Index (q,f) & LE p,q,f /. (Index (p,f)),f /. ((Index (p,f)) + 1) ) ) by A5;
case A11: Index (p,f) < Index (q,f) ; :: thesis: not p = f . (len f)
assume A12: p = f . (len f) ; :: thesis: contradiction
(Index (p,f)) + 1 <= Index (q,f) by ;
then len f <= Index (q,f) by A1, A9, A12, Th12;
hence contradiction by A3, Th8; :: thesis: verum
end;
case A13: ( Index (p,f) = Index (q,f) & LE p,q,f /. (Index (p,f)),f /. ((Index (p,f)) + 1) ) ; :: thesis: not p = f . (len f)
A14: now :: thesis: not p = f . ((Index (p,f)) + 1)
q in LSeg ((f /. (Index (p,f))),(f /. ((Index (p,f)) + 1))) by A13;
then consider r being Real such that
A15: q = ((1 - r) * (f /. (Index (p,f)))) + (r * (f /. ((Index (p,f)) + 1))) and
A16: 0 <= r and
A17: r <= 1 ;
A18: p = 1 * p by RLVECT_1:def 8
.= (0. ()) + (1 * p) by RLVECT_1:4
.= ((1 - 1) * (f /. (Index (p,f)))) + (1 * p) by RLVECT_1:10 ;
assume A19: p = f . ((Index (p,f)) + 1) ; :: thesis: contradiction
then p = f /. ((Index (p,f)) + 1) by ;
then 1 <= r by A13, A15, A16, A18;
then r = 1 by ;
hence contradiction by A4, A7, A19, A15, A18, FINSEQ_4:15, NAT_1:11; :: thesis: verum
end;
assume p = f . (len f) ; :: thesis: contradiction
hence contradiction by A1, A9, A14, Th12; :: thesis: verum
end;
end;
end;
then L_Cut (f,p) is_S-Seq_joining p,f /. (len f) by A1, A2, Th33;
then A20: (L_Cut (f,p)) . 1 = p ;
now :: thesis: ( ( Index (p,f) < Index (q,f) & ex i1 being Nat st
( 1 <= i1 & i1 + 1 <= len (L_Cut (f,p)) & q in LSeg ((L_Cut (f,p)),i1) ) ) or ( Index (p,f) = Index (q,f) & LE p,q,f /. (Index (p,f)),f /. ((Index (p,f)) + 1) & ex i1 being Nat st
( 1 <= i1 & i1 + 1 <= len (L_Cut (f,p)) & q in LSeg ((L_Cut (f,p)),i1) ) ) )
per cases ( Index (p,f) < Index (q,f) or ( Index (p,f) = Index (q,f) & LE p,q,f /. (Index (p,f)),f /. ((Index (p,f)) + 1) ) ) by A5;
case Index (p,f) < Index (q,f) ; :: thesis: ex i1 being Nat st
( 1 <= i1 & i1 + 1 <= len (L_Cut (f,p)) & q in LSeg ((L_Cut (f,p)),i1) )

then q in L~ (L_Cut (f,p)) by A2, A3, Th29;
hence ex i1 being Nat st
( 1 <= i1 & i1 + 1 <= len (L_Cut (f,p)) & q in LSeg ((L_Cut (f,p)),i1) ) by SPPOL_2:13; :: thesis: verum
end;
case ( Index (p,f) = Index (q,f) & LE p,q,f /. (Index (p,f)),f /. ((Index (p,f)) + 1) ) ; :: thesis: ex i1 being Nat st
( 1 <= i1 & i1 + 1 <= len (L_Cut (f,p)) & q in LSeg ((L_Cut (f,p)),i1) )

then q in L~ (L_Cut (f,p)) by A2, A3, A4, Th31;
hence ex i1 being Nat st
( 1 <= i1 & i1 + 1 <= len (L_Cut (f,p)) & q in LSeg ((L_Cut (f,p)),i1) ) by SPPOL_2:13; :: thesis: verum
end;
end;
end;
then A21: q in L~ (L_Cut (f,p)) by SPPOL_2:17;
then A22: Index (q,(L_Cut (f,p))) < len (L_Cut (f,p)) by Th8;
1 <= Index (q,(L_Cut (f,p))) by ;
then 1 <= len (L_Cut (f,p)) by ;
then p = (L_Cut (f,p)) /. 1 by ;
hence B_Cut (f,p,q) is_S-Seq_joining p,q by A1, A2, A4, A6, A10, A21, A20, Th32, Th34; :: thesis: verum