Syntax

#include <math.h>
double _j0(double x);
double _j1(double x);
double _jn(int n, double x);
double _y0(double x);
double _y1(double x);
double _yn(int n, double x);

Bessel functions solve certain types of differential equations. The _j0, _j1, and _jn functions are Bessel functions of the first kind for orders 0, 1, and n, respectively.

The _y0, _y1, and _yn functions are Bessel functions of the second kind for orders 0, 1, and n, respectively. The argument x must be positive. The argument n should be greater than or equal to zero. If n is less than zero, it will be a negative exponent.

For _j0, _j1, _y0, or _y1, if the absolute value of x is too large, the function sets errno to ERANGE, and returns 0. For _y0, _y1, or _yn, if x is negative, the function sets errno to EDOM and returns the value -HUGE_VAL. For _y0, _y1, or _yn, if x causes an overflow, the function sets errno to ERANGE and returns the value -HUGE_VAL.

This example computes y to be the order 0 Bessel function of the first kind for x, and z to be the order 3 Bessel function of the second kind for x.

#include <stdio.h>
#include <math.h>

int main(void)
{
   double x,y,z;

   x = 4.27;
   y = j0(x);      /* y = -0.3660 is the order 0 bessel                       */
                   /* function of the first kind for x                        */

   printf("j0( 4.27 ) = %5.4f\n", y);
   z = yn(3, x);   /* z = -0.0875 is the order 3 bessel                       */
                   /* function of the second kind for x                       */

   printf("yn( 3,4.27 ) = %5.4f\n", z);
   return 0;

   /****************************************************************************
      The output should be:

      j0( 4.27 ) = -0.3660
      yn( 3,4.27 ) = -0.0875
   ****************************************************************************/
}

• erf - erfc
  
• gamma

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