Question

How to Define a function named calculatePI that takes a positive integer n as its argument and calculates π using the formula: (Assume n is odd, which is the precondition of the function. And, this function should return double type value.) π = 4*(1 – 1/3 + 1/5 – 1/7 + 1/9 – 1/11 + ... 1/n)

Answer 1

#include <iostream>

using namespace std;

double calculatePI(int n) {
    int i;
    double pi = 0, sign = 1;
    for (i = 0; i < n; ++i) {
        pi += sign * (1.0 / (2 * i + 1));
        sign *= -1;
    }
    return 4*pi;
}

int main() {
    cout << "Value of PI is " << calculatePI(10000) << endl;
    return 0;
}