reserve p,q,r for FinSequence,
  x,y for object;

theorem Th15:
  for R being Relation, a,b being object st [a,b] in R holds R reduces a,b
proof
  let R be Relation, a,b be object;
  assume [a,b] in R;
  then reconsider p = <*a,b*> as RedSequence of R by Th7;
  take p;
  len p = 2 by FINSEQ_1:44;
  hence thesis;
end;
