#include <iostream>
#include <cmath>
#include <fstream>
using namespace std;
double const Pi = 4 * atan(1);

int main() {
	double calcPi = 0;
	double error = 0;
	ofstream outfile("c:PiA.txt", ios::out);
	outfile << "N" << "\t" << "Approximate Value" << "\t" << "Actual Value" << "\t" << "Percent Error" << endl;

	for (int k = 0; k <= 15; k++)
	{
		calcPi = calcPi + (pow(-1.0, k) * (4.0 / ((2.0 * k) + 1.0)));
		error = (((calcPi - Pi) * 100) / Pi);
		cout << "At k = " << k << ", the approximation for Pi is " << calcPi << " and the percent error is " << error << endl;
		outfile << k << "\t" << calcPi << "\t" "\t" "\t" << Pi << "\t" "\t" << error << endl;
	}
	return 0;
}