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

#define ACC 1e-3

double func(double x);
double funcd(double x);
double neuton(double x);
int main(int argc,char** argv)
{
printf("%d回", get_acc(12.0,ACC));
}
int get_acc(double _x, double acc){
int i=0;double x=_x;
printf("%lf\n",x);
while(fabs(neuton(x)-x)>acc){
x=neuton(x);i++;
printf("%lf\n",x);
}
printf("func(%lf)=%lf\n",x,func(x));
return i;
}

double func(double x)
{return (3*sin(x)+log(x));}
double funcd(double x)
{return (3*cos(x)+1/x);}
double neuton(double x)
{return (x-func(x)/funcd(x));}

こういうこと？