
theorem
  for G1, G2 being Group for H1, H2 being Subgroup of G1 for f being
Function of the carrier of G1, the carrier of G2 for A being Subset of G1 st A
= (the carrier of H1) \/ the carrier of H2 holds f.:the carrier of H1 "\/" H2 =
  f.:the carrier of gr A by Th4;
