theorem Th62:
  [:P,Q:] c= Indices A & (card Q=0 implies card P = 0) implies
  Segm(A,P,Q) = Segm(A@,Q,P)@
proof
  rng Sgm Q=Q & rng Sgm P=P by FINSEQ_1:def 14;
  hence thesis by Th19;
end;
