Mathc initiation/c33a3

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	x_dydx.h

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

double (*P_ay)(double x),
double (*P_by)(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                {m = 2.;}

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

  return( ((((*P_by)( x))-((*P_ay)( x)))*M) / (2*ny) );
}
/* ---------------------------------- */
double trapezoid_dydx(
double (*P_f)(double x, double y),
   
double (*P_ay)(double x),
double (*P_by)(double x),
   int     ny,

double ax,
double bx,
   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                 {m = 2.;}

  M += m * int_dy((*P_f), (*P_ay),(*P_by),ny, (ax+i*(bx-ax)/nx));
 }                       

  return( ((bx-ax)*M) / (2*nx) );
}
/* ---------------------------------- */
/* ---------------------------------- */

Les fonctions pour calculer les intégrales de la forme dydx.

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