/* ---------------------------------- */
/* save as fb.h                    */
/* ---------------------------------- */
double M(
double x,
double y,
double z)
{
      return( (x) );
}
char  Meq[] = "x";
/* ---------------------------------- */
double N(
double x,
double y,
double z)
{
      return( (y) );
}
char  Neq[] = "y";
/* ---------------------------------- */
double P(
double x,
double y,
double z)
{
      return( (z) );
}
char  Peq[] = "z";
/* ---------------------------------- */
double f(
double x,
double y)
{
      return( (1-x*x-y*y) );
}
char  feq[] = "1-x**2-y**2";
/* ---------------------------------- */
double u(
double x)
{
 return(       -sqrt(1-x*x) );
}
char  ueq[] = "-sqrt(1-x**2)";
/* ---------------------------------- */
double v(
double x)
{
 return(       sqrt(1-x*x)  );
}
char  veq[] = "+sqrt(1-x**2)";
/* ---------------------------------- */
/* ---------------------------------- */