Re: A question regarding a hyperbolic geometric function

*To*: mathgroup at smc.vnet.net*Subject*: [mg86414] Re: A question regarding a hyperbolic geometric function*From*: "David W.Cantrell" <DWCantrell at sigmaxi.net>*Date*: Tue, 11 Mar 2008 02:55:24 -0500 (EST)*References*: <fr2mhu$o5p$1@smc.vnet.net>

"Ali K. Ozdagli" <ozdagli at gmail.com> wrote: > Hi, > > I am working with Mathematica in order to solve an ordinary > differential equation with several boundary conditions. It turned out > that the solution is Kummer confluent hypergeometric function, > HyperGeometric1F1[a,b,x]. My problem is that for the values of a, b > and x I am interested in, e.g. a=-26.9, b=-20.1, x=300000, the > numerical accuracy of Mathematica is very poor. > > Can somebody suggest me a way to improve the mathematical accuracy of > HyperGeometric1F1? I prefer a quick and easy way but also appreciate > any hard way. I don't know if you're right or wrong. But as an example, let's use the values you mentioned above for a, b and x. In version 6.0.2, I get In[15]:= N[Hypergeometric1F1[-269/10, -201/10, 300000], 14] Out[15]= 2.9932104092161 * 10^130260 Is that very poor numerical accuracy? If so, what should Out[15] have been? David