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

theorem
  z2 <> 0.F_Complex & z1 / z2 = 1.F_Complex implies z1 = z2
proof
  reconsider z19=z1,z29=z2 as Element of COMPLEX by Def1;
  assume
A1: z2 <> 0.F_Complex;
  assume z1 / z2 = 1.F_Complex;
  then z19 / z29 = 1.F_Complex by A1,Th6;
  then z19 / z29 = 1 by Def1;
  hence thesis by XCMPLX_1:58;
end;
