theorem Th8:
  for R being Relation holds <*x, y*> is RedSequence of R implies [x, y] in R
proof
  let R be Relation;
  set P = <*x, y*>;
A1: P.1 = x & P.2 = y;
  len P = 2 by FINSEQ_1:44;
  then 1 in dom P & 1 + 1 in dom P by FINSEQ_3:25;
  hence thesis by A1,REWRITE1:def 2;
end;
