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/ε. Here, ε is the machine precision, ε = 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

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