This function evaluates the modified Bessel function of the second kind of order zero.

Function Return Value

BSK0 — Function value.   (Output)

Required Arguments

X — Argument for which the function value is desired.   (Input)

 

Generic:                              BSK0 (X)

Specific:                             The specific interface names are S_BSK0 and D_BSK0.

FORTRAN 77 Interface

Single:                                BSK0 (X)

Double:                              The double precision function name is DBSK0.

Description

The Bessel function K0(x) is defined to be

The argument must be larger than zero, but not so large that the result, approximately equal to

underflows.

Figure 6- 4  Plot of K0(x) and K1(x)

Comments

Informational error

Type Code

2         1                  The function underflows because X is too large.

Example

In this example, K0(0.5) is computed and printed.

 

      USE BSK0_INT

      USE UMACH_INT

 

      IMPLICIT   NONE

!                                 Declare variables

      INTEGER    NOUT

      REAL       VALUE, X

!                                 Compute

      X     = 0.5

      VALUE = BSK0(X)

!                                 Print the results

      CALL UMACH (2, NOUT)

      WRITE (NOUT,99999) X, VALUE

99999 FORMAT (' BSK0(', F6.3, ') = ', F6.3)

      END

Output

 

BSK0( 0.500) =  0.924

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