# yn(3M)

## NAME

y0, y1, yn - Bessel functions of the second kind

## SYNOPSIS

cc [ *flag* ... ] *file* ... -lm [ *library* ... ]
double y0(double *x*);
double y1(double *x*);
double yn(int *n*, double *x*);

## DESCRIPTION

The y0(), y1() and yn() functions compute Bessel functions
of *x* of the second kind of orders 0, 1 and *n* respectively.
The value of *x* must be positive.

## RETURN VALUES

Upon successful completion, y0(), y1() and yn() will return
the relevant Bessel value of *x* of the second kind.
If *x* is NaN, NaN is returned.
If the *x* argument to y0(), y1() or yn() is negative,
-HUGE_VAL or NaN is returned, and *errno* may be set to EDOM.
If *x* is 0.0, -HUGE_VAL is returned and *errno* may be set to
ERANGE or EDOM.
If the correct result would cause overflow, -HUGE_VAL is
returned and errno may be set to ERANGE.
For exceptional cases, **matherr(3M)** tabulates the values to
be returned as dictated by Standards other than XPG4.

## ERRORS

The y0(), y1() and yn() functions may fail if:
EDOM The value of *x* is negative.
ERANGE
The value of *x* is too large in magnitude, or *x* is 0.0,
or the correct result would cause overflow.

## USAGE

An application wishing to check for error situations should
set *errno* to 0 before calling y0(), y1() or yn(). If *errno*
is non-zero on return, or the return value is NaN, an error
has occurred.

## ATTRIBUTES

See **attributes(5)** for descriptions of the following attri-
butes:
____________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
|_____________________________*|*_____________________________*|*
| MT-Level | MT-Safe |
|_____________________________*|*_____________________________*|*

## SEE ALSO

**isnan(3M)**, **j0(3M)**, **matherr(3M)**, **attributes(5)**, **standards(5)**

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