/* --------------------------------- */
/* save as fa.h                      */
/* --------------------------------- */
double f(
double x,
double y)
{
 return(       (y*y * sin(x*y)) );
}
char  feq[] = "y**2 * sin(x*y)";
/* --------------------------------- */
double f_x(
double x,
double y)
{
 return(       (y*y*y * cos(x*y)) );
}
char Dfeq_x[] = "y**3 * cos(x*y)";
/* --------------------------------- */
double f_y(
double x,
double y)
{
 return(        (x* y*y * cos(x*y) + 2*y * sin(x*y))  );
}
char Dfeq_y[] = "x*y**2 * cos(x*y) + 2*y * sin(x*y)";
/* --------------------------------- */
double f_xx(
double x,
double y)
{
 return(    ( -y*y*y*y * sin(x*y) ) );
}
char Dfeq_xx[] = "-y**4 * sin(x*y)";
/* --------------------------------- */
double f_yy(
double x,
double y)
{
 return(        (4*cos(x*y)*x*y + 2*sin(x*y) - y*y*sin(x*y)*x*x)  );
}
char Dfeq_yy[] = "4*cos(x*y)*x*y + 2*sin(x*y) - y**2*sin(x*y)*x**2";
/* --------------------------------- */