reserve a,b,c,d for Real;
reserve z,z1,z2 for Complex;

theorem Th33:
  (-z)*' = -(z*')
proof
  thus Re ((-z)*') = Re -z by Th27
    .= - Re z by Th17
    .= - Re (z*') by Th27
    .= Re -(z*') by Th17;
  thus Im ((-z)*') = -Im -z by Th27
    .= - -Im z by Th17
    .= - Im (z*') by Th27
    .= Im -(z*') by Th17;
end;
