This function evaluates the Kelvin function of the first kind, bei, of order zero.

Function Return Value

BEI0 — Function value.   (Output)

Required Arguments

X — Argument for which the function value is desired.   (Input)
ABS(X) must be less than 119.

FORTRAN 90 Interface

Generic:                              BEI0 (X)

Specific:                             The specific interface names are S_BEI0 and D_BEI0.

FORTRAN 77 Interface

Single:                                BEI0 (X)

Double:                              The double precision name is DBEI0.

Description

The Kelvin function bei0(x) is defined to be ℑJ0(xe3πi∕4). The Bessel function J0(x) is defined in BSJ0. Function BEI0 is based on the work of Burgoyne (1963).

In BEI0, x must be less than 119.

Example

In this example, bei0(0.4) is computed and printed.

 

      USE BEI0_INT

      USE UMACH_INT

 

      IMPLICIT   NONE

!                                 Declare variables

      INTEGER    NOUT

      REAL       VALUE, X

!                                 Compute

      X     = 0.4

      VALUE = BEI0(X)

!                                 Print the results

      CALL UMACH (2, NOUT)

      WRITE (NOUT,99999) X, VALUE

99999 FORMAT (' BEI0(', F6.3, ') = ', F6.3)

      END

Output

 

BEI0( 0.400) =  0.040

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