Mathematics has formed a special science in asking and answering questions. In the history of mathematical development, there are many examples to show that mathematical problems are the main source of mathematical development. Mathematicians spend a lot of energy and time to solve these problems. Although there are still some unanswered questions, in the process, they have created many new concepts, theories and methods, which are the most valuable things in mathematics. ◇ Before 600 BC ◇ According to "Dead Bodies" written by China during the Warring States Period: "The ancients (note: the legendary Huangdi or Shi Yao people) were rules, moments, accuracy and ropes, which made the world imitate", which was equivalent to "round, square, flat and flat" before 2500 BC.