j0, j1, jn - Bessel functions of first kind

Syntax	#include <math.h> double j0(double x); double j1(double x); double jn(int n, double x);
Description	j0(), j1() and jn() compute the Bessel functions of the first kind for floating-point valuesx and the integer orders 0, 1 or n.
Return val.	Bessel value of x if successful.
See also	y0(), y1(), yn(), math.h.