theorem Th60:
  for F be FinSequence of D,i,P st not i in P & [:P,Q:] c= Indices A9
  holds Segm(A9,P,Q) = Segm(RLine(A9,i,F),P,Q)
proof
  let F be FinSequence of D,i,P such that
A1: not i in P and
A2: [:P,Q:] c= Indices A9;
  rng Sgm Q=Q & rng Sgm P=P by FINSEQ_1:def 14;
  hence thesis by A1,A2,Th38;
end;
