reserve a,b for Complex;
reserve z for Complex;
reserve n0 for non zero Nat;

theorem Th7:
  (n0-root z)|^n0 = z
proof
  reconsider n=n0 as Element of NAT by ORDINAL1:def 12;
  thus (n0-root z)|^n0 = ((n-real-root |.z.|)*cos((Arg z+2*PI*0)/n) + (n
  -real-root |.z.|)*sin((Arg z+2*PI*0)/n)*<i>)|^n
    .= z by POLYEQ_3:34;
end;
