Area de un circulo con clases y objetos

#include <iostream>
using namespace std;

class Area {
    public:
        void circle(double rad) {
            double area = 3.1416 * rad * rad;
            cout << "Area = " << area << endl;
        }
};

int main() {
    Area obj;
    double radius;
    
    cout << "Enter Radius: ";
    cin >> radius;
    
    obj.circle(radius);
    
    return 0;
}