Numerical differential with 2 point

diffsin_2point.c

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