reserve i,j,k for Nat;

theorem Th7:
  for K being left_zeroed right_zeroed non empty addLoopStr holds
  the_unity_wrt the addF of K = 0.K
proof
  let K be left_zeroed right_zeroed non empty addLoopStr;
  reconsider e=0.K as Element of K;
  e is_a_unity_wrt the addF of K by Th6;
  hence thesis by BINOP_1:def 8;
end;
