[c++] no matching function for call to ' '

I was given to implement the function:

 "static double distanta (const Complex&, const Complex&);"

which return the distance between two Complex numbers. The definition of the function it is inside the Complex class and I have implemented it like that:

double Complex::distanta(const Complex &a, const Complex &b)
{    
    double x = a.real() - b.real();
    double y = a.imag() - b.imag();

    return sqrt(x * x + y * y);
}

As far as I know a static function can only access static members and my class only has

double _re;
double _im;

as data members.

Within the main function I have called it as:

#include <iostream>
#include "complex.h"

using namespace std;

int main()
{
    Complex* firstComplexNumber; 
    firstComplexNumber = new Complex(81, 93);

    cout << "Numarul complex este: " << *firstComplexNumber << endl;

    Complex* secondComplexNumber;
    secondComplexNumber = new Complex(31, 19);

    cout << "Distanta dintre cele doua numere" <<endl << endl;
    Complex::distanta(firstComplexNumber, secondComplexNumber);
    return 0;
}

and the error I get is:

error: no matching function for call to 'Complex::distanta(Complex*&, Complex*&)'

Could you please tell me what is it that I'm doing wrong? Thanks!

You are trying to pass pointers (which you do not delete, thus leaking memory) where references are needed. You do not really need pointers here:

Complex firstComplexNumber(81, 93);
Complex secondComplexNumber(31, 19);

cout << "Numarul complex este: " << firstComplexNumber << endl;
//                                  ^^^^^^^^^^^^^^^^^^ No need to dereference now

// ...

Complex::distanta(firstComplexNumber, secondComplexNumber);