theorem Th39:
  for T being TopaddGroup st for a being Element of T, W being
  a_neighborhood of -a ex A being a_neighborhood of a st -A c= W holds T is
  UnContinuous
proof
  let T be TopaddGroup such that
A1: for a being Element of T, W being a_neighborhood of -a ex A being
  a_neighborhood of a st -A c= W;
  set f = add_inverse T;
  for W being Point of T, G being a_neighborhood of f.W ex H being
  a_neighborhood of W st f.:H c= G
  proof
    let a be Point of T, G be a_neighborhood of f.a;
    f.a = -a by Def6;
    then consider A being a_neighborhood of a such that
A2: -A c= G by A1;
    take A;
    thus thesis by A2,Th9;
  end;
  hence f is continuous by BORSUK_1:def 1;
end;
