reserve z,z1,z2,z3,z4 for Element of F_Complex;

theorem
  -z = (-1_F_Complex) * z
proof
  reconsider z9=z as Element of COMPLEX by Def1;
A1: -1r = -1_F_Complex by Lm1,Th2;
  thus -z = -z9 by Th2
    .= (-1_F_Complex) * z by A1;
end;
