FNbessI0

Routine

double FNbessI0 (double x)

Purpose

Evaluate the zeroth-order modified Bessel function of first kind

Description

This function returns the value of the zero'th order modified Bessel function of the first kind. This function is defined as 
            1   2 pi
  I0(z) = ----  Int exp (z cos(a)) da.
          2 pi   0
This routine calculates an approximation using an infinite series. This series is rapidly converging for moderate values of z.

Parameters

<- double FNbessI0
Returned value
-> double x
Input value

Author / revision

P. Kabal / Revision 1.3 2003/05/09

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