Mathc initiation/a286

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	x_dydx.h

/* ---------------------------------- */
/* save as x_dydx.h                   */
/* ---------------------------------- */
double int_dy(
double (*P_f)(double x, double y),

double (*Py0)(double x),
double (*Py1)(double x),
   int   ny,
   
double    x
)
{
   int i = 0;
double m = 0.;
double M = 0.;

 for(i = 0; i <= ny; i++)
 {
       if(i ==0 || i== ny){m = 1.;}
  else if(fmod(i,2) == 0) {m = 2.;}
  else                    {m = 4.;}

  M += m * (*P_f)(x,  ((*Py0)(x)) + i*(((*Py1)(x))-((*Py0)(x)))/ny);
 }

  return( ((((*Py1)(x)) -((*Py0)(x)))*M) / (3*ny) );
}
/* ---------------------------------- */
double simpson_dydx(
double (*P_f)(double x, double y),
   
double (*Py0)(double x),
double (*Py1)(double x),
   int   ny,

double   x0,
double   x1,
   int   nx
)
{
   int i = 0;
double m = 0.;
double M = 0.;

 for(i = 0; i <= nx; i++)
 {
       if(i ==0 || i== nx){m = 1.;}
  else if(fmod(i,2) == 0) {m = 2.;}
  else                    {m = 4.;}

  M += m * int_dy((*P_f),  (*Py0),(*Py1),ny, (x0 + i*(x1-x0)/nx));
 }

  return( ((x1 -x0)*M) / (3*nx) );
}
/* ---------------------------------- */
/* ---------------------------------- */

Les fonctions pour calculer les intégrales de la forme dydx.