Xref: utzoo sci.math.num-analysis:1157 comp.lang.fortran:3844 sci.math:12475
Path: utzoo!attcan!uunet!ns-mx!l_eld09.icaen.uiowa.edu
From: jlhaferman@l_eld09.icaen.uiowa.edu (Jeffrey Lawrence Haferman)
Newsgroups: sci.math.num-analysis,comp.lang.fortran,sci.math
Subject: Complex trig functions for large imaginary arguments
Message-ID: <2423@ns-mx.uiowa.edu>
Date: 24 Sep 90 17:24:51 GMT
Sender: news@ns-mx.uiowa.edu
Followup-To: sci.math.num-analysis
Lines: 25


I need to calculate the sine and cosine of some complex numbers
where the imaginary part may get as large as 10^3 in magnitude.
Because of the factor exp(y) (where y is the imaginary part
of the given complex number) needed to calculate the cosine (sine),
this problem will exceed the limits of most computers standard
arithmetic libraries.

What I would like is a quick and easy fix - 

  - perhaps an arbitrary precision (fortran) math library
    exhists somewhere?

A little background on the problem:
   I'm working with an existing program which needs to
   calculate logarithmic derivatives and Ricatti-Bessel
   functions using complex arguments, and the complex trig
   functions are needed for those calculations, I believe.
   I don't know much about the theory underlying the computer
   code, and hopefully I won't have to get into it right now.
   
Jeff Haferman                            internet: jlhaferman@icaen.uiowa.edu
Department of Mechanical Engineering
University of Iowa
Iowa City IA  52240