theorem
  for V be Abelian add-associative right_zeroed right_complementable
non empty addLoopStr, v1,v2 be Element of V holds v1 <> v2 implies Sum{v1,v2}
  = v1 + v2
proof
  let V be Abelian add-associative right_zeroed right_complementable non
  empty addLoopStr, v1,v2 be Element of V;
  assume v1 <> v2;
  then
A1: <* v1,v2 *> is one-to-one by FINSEQ_3:94;
  rng<* v1,v2 *> = {v1,v2} & Sum<* v1,v2 *> = v1 + v2 by FINSEQ_2:127
,RLVECT_1:45;
  hence thesis by A1,Def2;
end;
