#include <iostream>
#include <cmath>
#include <iomanip>
 
using namespace std;
 
long double f(long double x) {
    return sqrt(1.0L - x * x);
}
 
int main() {
    const int n = 1000000;   // więcej podziałów = większa dokładność
    long double a = -1.0L;
    long double b = 1.0L;
    long double h = (b - a) / n;
 
    long double suma = 0.0L;
 
    for(int i = 0; i < n; i++) {
        long double x = a + i * h;
        suma += f(x);
    }
 
    long double pi = 2.0L * h * suma;
 
    cout << fixed << setprecision(20);
    cout << "Pi (metoda prostokatow): " << pi << endl;
 
    return 0;
}

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