Qi County, Kaifeng Qi County, Kaifeng Qi County or Qixian () is a county of Kaifeng, Henan, People's Republic of China, with an area of 1243 square km and a population of 1.05 million. From Shang to Western Zhou, Qi County was the place of the State of Qi. In Qin Dynasty, Qi was named as Yongqiu (Chinese: 雍丘). It was the site of the Battle of Yongqiu in 756. In Song Dynasty, Yongqiu was renamed to Qi. Cai Wenji, a Han Dynasty poet and composer,was born shortly before 178 in Yu Prefecture (), Chenliu Commandery (), in what is now Qi County,
What Is Mathematics? Expectations" by Charles Dickens. According to Constance Reid, Courant finalized the title after a conversation with Thomas Mann. What Is Mathematics? What Is Mathematics? is a mathematics book written by Richard Courant and Herbert Robbins, published in England by Oxford University Press. It is an introduction to mathematics, intended both for the mathematics student and for the general public. First published in 1941, it discusses number theory, geometry, topology and calculus. A second edition was published in 1996 with an additional chapter on recent progress in mathematics, written by Ian Stewart. The book was based on Courant's course material. Although