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

#define N 1000

double f(double x)
{
	return 1/x;
}

int main(void)
{
	int i;
	double h,soma=0.0f;

	h=(1.0-0.1)/N;

	for (i=0;i<N;i++)
	{
		double x = 0.1 + h*i;
		soma += h*f(x);
	}

	double e = fabs((-log(0.1)-soma)/-log(0.1));

	printf("Valor calculado: %.15e \nValor real: %.15e \n",soma,-log(0.1));
	printf("Erro: %e % \n",e*100);

	return 0;
}

// I(a,b) = h*sum_i ( f(x_i) )
// erro = h/2 * [f(b)-f(a)]
// erro ~ 1/N