Since the discovery of the root number two, the first mathematical crisis was marked by the emergence of the definition of irrational numbers. German mathematician Dai Dejin started from the requirement of continuity and used rational numbers? Split? Define irrational numbers and base the real number theory on strict science, so that irrational numbers can be counted? Irrational? The era has also ended the first great crisis in the history of mathematics that lasted for more than 2000 years.