derivative with respect to a particular D of X output value of the cost function and we set it equal to zero it's pretty straightforward to take those derivatives and then from there it's straightforward algebra to solve this stationarity condition and what we get is that the optimal discrimination function is the ratio between P data of X and the sum of P data of X and P model of X so this is the main mathematical technique that sets generative adverse own networks apart from the other models that I described in the family tree