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

#define   E     0.5
#define   M     2.2
#define   EPS   1e-15

double   kepler(double x).
double   root(double f(double x), double a, double b);

int main(void)
{
   double   x;
   
   x = root(kepler, -100.0, +100.0);
   printf("%s%.16f\n%s%.16f\n\n",
      "Approximate root: ", x,
      "  Function value: ", kepler(x));
   return 0;
}

double kepler(double x)
{
   return (x - E * sin(x) - M);
}

double root(double f(double x), double a, double b)
{
   double   m = (a + b) / 2.0;     /* mpoint */

   if (f(m) == 0.0 || b - a < EPS)
      return m;
   else if (f(a) * f(m) < 0.0)
      return root(f, a, m);
   else
      return root(f, m, b);
}