Hi, > An approximation to tanh(x) is a continued fraction > x/1+ (x^2)/3+ (4x^2)/5+ (16x^2)/9+ ... are you sure this is correct? Another well-known formulation is x/(1+x^2/(3+x^2/(5+x^2/(7+..... which works for me and converges quickly. see http://nrich.maths.org/public/viewer.php?obj_id=1451 gr~~~