
theorem Th5:
  for D being set, p, q being FinSequence of D holds
    Union (p^q) = Union p \/ Union q
proof
  let D be set, p, q be FinSequence of D;
  union rng(p^q) = union (rng p \/ rng q) by FINSEQ_1:31
    .= Union p \/ Union q by ZFMISC_1:78;
  hence thesis;
end;
