BSY1

This function evaluates the Bessel function of the second kind of order one.

Function Return Value

BSY1 — Function value. (Output)

Required Arguments

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

FORTRAN 90 Interface

Generic: BSY1 (X)

Specific: The specific interface names are S_BSY1 and D_BSY1.

FORTRAN 77 Interface

Single: BSY1 (X)

Double: The double precision function name is DBSY1.

Description

The Bessel function Y1(x) is defined to be

 

 

Y1(x) is defined for x > 0. To prevent the answer from being less accurate than half precision, x should be smaller than

 

For the result to have any precision at all, ∣x∣ must be less than 1/ɛ. Here, ɛ is the machine precision, ɛ = AMACH(4).

Example

In this example, Y1(3.0) is computed and printed.

 

USE BSY1_INT

USE UMACH_INT

 

IMPLICIT NONE

! Declare variables

INTEGER NOUT

REAL VALUE, X

! Compute

X = 3.0

VALUE = BSY1(X)

! Print the results

CALL UMACH (2, NOUT)

WRITE (NOUT,99999) X, VALUE

99999 FORMAT (' BSY1(', F6.3, ') = ', F6.3)

END

Output

 

BSY1( 3.000) = 0.325