Untitled

CODE:

file: Pi.h

class Pi {
    public:
        Pi(const int nTerms);
        double apprErr();
        void print();
        
    private:
        int n;
        double value();
        
};

file: Pi.cpp (I've written the main function in this file)

#include<iostream>
#include <cmath>
#include "Pi.h"

using namespace std;

Pi::Pi(const int nTerms) {
    n = nTerms;
}

double Pi::apprErr() {
    return abs(M_PI - value());
}

void Pi::print() {
    cout << "Pi with "<< n << " terms: ";
    cout << value();
    cout << endl;
}
        
double Pi::value() {
    double pi = 0.0;
    int divisor = 1;
    for(int i =1; i <= n; i++) {
        if (i%2 == 1) {
            pi += (4/(double)divisor);
        } else {
            pi -= (4/(double)divisor);
        }
        divisor += 2;
    }
    return pi;
}

int main() {
    Pi pi1(3);
    pi1.print();
    cout << pi1.apprErr();
    return 0;
}

Sample output:

Pi with 3 terms: 3.46667
0.325074

* Go through the code and try executing them, you'll understand them.

* Hope my response got you what you're looking for (If it did, please do Upvote!). If you have any doubt while grasping the code, feel free to ask.

Happy coding. :)