Complex Number in C++ Static

#include <iostream>
#include <cstdlib>
#include <cmath>

using namespace std;

class Complex{
    double real;
    double img;
public:
    Complex();
    Complex(double, double);
    void input();
    Complex add(Complex, Complex);
    Complex add(Complex, Complex, Complex);
    Complex subtract(Complex, Complex);
    Complex subtract(Complex, Complex, Complex);
    Complex multiply(Complex,Complex);
    Complex multiply(Complex,Complex, Complex);
    Complex divide(Complex, Complex);
    Complex divide(Complex, Complex, Complex);
    void display();
    ~Complex();
};

Complex::~Complex(){

}

Complex::Complex(){
    real = 0.0;
    img = 0.0;
}

Complex::Complex(double real, double img){
    this->real = real;
    this->img = img;
}

void Complex::input(){
    cout << "Enter the real part: ";
    cin >> real;
    cout << "Enter the imaginary part: ";
    cin >> img;
}

Complex Complex::add(Complex num1, Complex num2){
    Complex result;
    result.real = num1.real + num2.real;
    result.img = num1.img + num2.img;
    return result;
}

Complex Complex::add(Complex num1, Complex num2, Complex num3){
    return add(add(num1, num2), num3);
}

Complex Complex::subtract(Complex num1, Complex num2){
    Complex result;
    result.real = num1.real - num2.real;
    result.img = num1.img - num2.img;
    return result;
}

Complex Complex::subtract(Complex num1, Complex num2, Complex num3){
    return subtract(subtract(num1, num2), num3);
}

Complex Complex::multiply(Complex num1, Complex num2){
    Complex result;
    result.real = (num1.real * num2.real) - (num1.img * num2.img);
    result.img = (num1.real * num2.img) + (num2.real * num1.img);
    return result;
}

Complex Complex::multiply(Complex num1, Complex num2, Complex num3){
    return multiply(multiply(num1, num2), num3);
}

Complex Complex::divide(Complex num1, Complex num2){
    Complex result;
    result.real = ((num1.real * num2.real) + (num1.img * num2.img))
                    /(pow(num2.real, 2) - pow(num2.img, 2));
    result.img = ((num2.real * num1.img) - (num1.real * num2.img))
                    /(pow(num2.real, 2) - pow(num2.img, 2));
    return result;
}

Complex Complex::divide(Complex num1, Complex num2, Complex num3){
    return divide(divide(num1, num2), num3);
}

void Complex::display(){
    cout << real << " + i" << img << endl;
}

int main() {
    system("cls");
    cout << "For complex number 1" << endl;
    Complex num1;double real, img;
    num1.input();
    cout << "For complex number 2" << endl;
    cout << "Enter the real part: ";
    cin >> real;
    cout << "Enter the imaginary part: ";
    cin >> img;
    Complex num2(real, img);
    Complex sum = num1.add(num1, num2);
    Complex diff = num1.subtract(num1, num2);
    Complex prod = num1.multiply(num1, num2);
    Complex quot = num1.divide(num1, num2);
    cout << "Sum" << endl;
    sum.display();
    cout << "Product" << endl;
    prod.display();
    cout << "Difference" << endl;
    diff.display();
    cout << "Division" << endl;
    quot.display();
    cin.ignore();
    cin.get();
    return 0;
}