April 19, 1991 J0 3

### NAME

j0, j0f, j1, j1f, jn, jnf, y0, y0f, y1, y1f, yn, ynf - Bessel functions of first and second kind

### LIBRARY

Math Library (libm, -lm)

### SYNOPSIS

```double` j0(```double x`)
```float` j0f(```float x`)
```double` j1(```double x`)
```float` j1f(```float x`)
```double` jn(```int n``, double x`)
```float` jnf(```int n``, float x`)
```double` y0(```double x`)
```float` y0f(```float x`)
```double` y1(```double x`)
```float` y1f(```float x`)
```double` yn(```int n``, double x`)
```float` ynf(```int n``, float x`)

### DESCRIPTION

The functions j0(``), j0f(``), j1(``) and j1f(``) compute the Bessel function of the first kind of the order 0 and the order 1, respectively, for the real value ```x`; the functions jn(``) and jnf(``) compute the Bessel function of the first kind of the integer order ```n` for the real value ```x`.

The functions y0(``), y0f(``), y1(``) and y1f(``) compute the linearly independent Bessel function of the second kind of the order 0 and the order 1, respectively, for the positive integer value ```x` (expressed as a double); the functions yn(``) and ynf(``) compute the Bessel function of the second kind for the integer order ```n` for the positive integer value ```x` (expressed as a double).

### RETURN VALUES

If these functions are successful, the computed value is returned, otherwise the global variable errno is set to ```EDOM` and a reserve operand fault is generated.

### SEE ALSO

math(3)

### HISTORY

This set of functions appeared in Version 7 `AT&T UNIX`.