How to output the number pi in C++?

Answer 1

Approximation without any methods etc..
cout << 22.0 / 7;

Answer 2

#define _USE_MATH_DEFINES
#include <math.h>

int main() {
cout << M_PI;
...

Answer 3

#include <iostream>
#include <cmath>
using namespace std;

int main() {
cout << atan(1)*4;
return 0;
}