theorem Th74:
  G,H are_isomorphic & G is finite implies H is finite
proof
  assume that
A1: G,H are_isomorphic and
A2: G is finite;
  consider h such that
A3: h is bijective by A1;
  rng h = the carrier of H by A3,FUNCT_2:def 3;
  hence thesis by A2;
end;
