Geocentric model knew about Tusi's work or that of the Maragha school. Not all Greeks agreed with the geocentric model. The Pythagorean system has already been mentioned; some Pythagoreans believed the Earth to be one of several planets going around a central fire. Hicetas and Ecphantus, two Pythagoreans of the 5th century BC, and Heraclides Ponticus in the 4th century BC, believed that the Earth rotated on its axis but remained at the center of the universe. Such a system still qualifies as geocentric. It was revived in the Middle Ages by Jean Buridan. Heraclides Ponticus was once thought to have proposed
Central limit theorem possible values. The law of large numbers as well as the central limit theorem are partial solutions to a general problem: "What is the limiting behaviour of as approaches infinity?" In mathematical analysis, asymptotic series are one of the most popular tools employed to approach such questions. Suppose we have an asymptotic expansion of : Dividing both parts by and taking the limit will produce , the coefficient of the highest-order term in the expansion, which represents the rate at which changes in its leading term. Informally, one can say: " grows approximately as ". Taking the difference between and