theorem Th16:
  for G being Fanoian add-associative right_zeroed
right_complementable non empty addLoopStr, x being Element of G holds x = -x
  implies x = 0.G
proof
  let G be Fanoian add-associative right_zeroed right_complementable non
  empty addLoopStr, x be Element of G;
A1: -x + x = 0.G by RLVECT_1:5;
  assume x = -x;
  hence thesis by A1,VECTSP_1:def 18;
end;
