1.10 jN, jNf, yN, yNf—Bessel functions

Synopsis

#include <math.h>
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 Bessel functions are a family of functions that solve the differential equation

  2               2    2
 x  y'' + xy' + (x  - p )y  = 0

These functions have many applications in engineering and physics.

jn calculates the Bessel function of the first kind of order n. j0 and j1 are special cases for order 0 and order 1 respectively.

Similarly, yn calculates the Bessel function of the second kind of order n, and y0 and y1 are special cases for order 0 and 1.

jnf, j0f, j1f, ynf, y0f, and y1f perform the same calculations, but on float rather than double values.

Returns
The value of each Bessel function at x is returned.

Portability
None of the Bessel functions are in ANSI C.