You are right about "Pade approximant", which is even better then "Chebyshev Approximation". I use the "Polynomial Approximation from Chebyshev Coefﬁcients" which are easy to determine. If you google at "numerical recipes in c pdf", you will find the PDF version of the book I use. In this document you find full documented C-functions of "Chebyshev Approximation", "Polynomial Approximation from Chebyshev Coefﬁcients", and of course "Pade approximant". You can copy and paste these functions directly from the PDF file, and you are in business in calculating your own polynomial coefficients. After