>>798
だいたいこんな感じ
#include <stdio.h>
#include <math.h>

#define f(x) (sin(2 * (x)) - 0.5) /* x = 0.5 */
#define g(x) (2 * cos(2 * (x)))

#define MAXCOUNT 10

int main(void)
{
double x = 0.5;
int k;

for (k = 1; k <= MAXCOUNT; k++) {
x = x - f(x) / g(x);
printf("%17.12f %15.8e\n", x, fabs(f(x)));
}

return 0;
}