Numerical differential with 3 point

diffsin_3point.c

#include<stdio.h>
#include<math.h>
int main(){
    double h = 1 / pow(2,16);
    double df = (2*sin(1+h) + 3*sin(1) - 6*sin(1-h) + sin(1 - 2*h) )/(6*h);
    printf("cos(1) = %.6f \nd/dx sin(1) = %.6f",cos(1),df);
    return 0;
}