Let be a polynomial and be maxroot the maximal modulus of the root of . From we may derive a polynomial such that the roots of have a modulus lower or equal to 1 and if is a root of then maxroot is a root of . The calculation of the coefficients of may be done with the procedure
int Unit_Polynom(int Degree,INTERVAL_VECTOR &Coeff, double maxroot,INTERVAL_VECTOR &CoeffU)where Coeff are the coefficients of and CoeffU the coefficients of . This procedure returns 1 if the calculation has been successfull, 0 otherwise.