#include <iostream>
#include <math.h>
#include <iomanip>



using namespace std;

#define PI 3.14159265

int main(){
	int n, k;
	double a, Pole, R_opisanego, R_wpisanego ;


	do {
		cout << "Podaj n: " << endl;
		cin >> n;
	} while (n < 4 || n > 100);

	do {
		cout << "Podaj k: " << endl;
		cin >> k;
	} while (k < 0 || k > 10);

	do {
		cout << "Podaj a: " << endl;
		cin >> a;
	} while (a <= 0.0 || a > 10.0);

	Pole = (n / 4)*(1/tan(PI / n))*a*a;
	//cout << "pole: " << Pole;

	R_opisanego = a /( 2 * sin(PI / n));
	//cout << "R_opisanego: " << R_opisanego;

	R_wpisanego = a /( 2 * tan(PI/n));

	//cout << "R_wpisanego: " << R_wpisanego << endl;

	cout << fixed << showpoint;
	cout << setprecision(k);
	cout << Pole << " ";
	cout << R_opisanego << " ";
	cout << R_wpisanego << " ";

	system("pause");
}