theorem Th33:
  x <> y implies <*x,y*> |-- y = {}
proof
  y in { x,y } by TARSKI:def 2;
  then
A1: y in rng<*x,y*> by Lm1;
  assume x <> y;
  then
A2: y..<*x,y*> = 2 by Th20;
  len<*x,y*> = 2 by FINSEQ_1:44;
  hence thesis by A1,A2,FINSEQ_4:49;
end;
