On 31.08.2012 13:51, firstname.lastname@example.org wrote: > Hi, > > I'm trying to approximate tan(x) using polynomial in the interval [-Pi/4, Pi/4]. > What is the best method to do this? > I searching I found Chebyshev, Talyor or any other method. > Thank you
Not sure what you mean by 'best' and why it should be polynomial. In that case try 'chebpade' or 'minmax' for [0 .. Pi/4] and do some corrections in the endpoints (use correct Digits:= ... ).
One classical is tan(x) ~ x + x^3 P(x^2)/Q(x^2) for that range, which is a rational function.