Calculates the value of PI

pi.cpp

#include<bits/stdc++.h>
using namespace std;

int main()
{
    double b, h, pi;
    pi = 2; // area of the rectangle
    b = 0.5 * sqrt(2.0); // initial base
    for(int i = 2; i <= 25; ++i)
    {
        h = 1 - sqrt(1 - x * x); // the height
        pi += pow(2, i) * b * h; // add the area
        b =  0.5 * sqrt(b * b + h * h); // the next base
    }
    printf("%.14f\n", pi);

    return 0;
}

https://medium.com/@dipu.sudipta/calculating-the-value-of-pi-%CF%80-from-basic-geometry-and-some-c-549e278afd03