Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2021/iii/paper-158/4/i/b/solution

Player II can force both parts of II's winning condition. First choose one coordinate reserved outside the coding of a fixed infinite descending chain and play . On the remaining reserved coordinates, play values that make the relation coded by contain that descending chain. Thus while for the chosen . Hence

New to topics? Read the docs here!