
theorem LMGSEQ4:
  for D be non empty set, x1,x2,x3,x4 be Element of D
  holds <* x1,x2,x3,x4 *> is Element of (4-tuples_on D)
proof
  let D be non empty set, x1,x2,x3,x4 be Element of D;
  reconsider x1234 = <* x1,x2,x3,x4 *> as FinSequence of D;
P1: len x1234 = 4 by FINSEQ_4:76;
  x1234 in D* by FINSEQ_1:def 11;
  then x1234 in 4-tuples_on D by P1;
  hence thesis;
end;
