What did Kangxi do in mathematics?

Professor Li said that it is not without historical basis to infer that the "quadrature method" was created by Emperor Kangxi. Because in many history books, there is a record that Emperor Kangxi "loves and is proficient in arithmetic".

As the king of a country, Kangxi's love for mathematics is rare in Chinese and foreign history. According to historical records, during the Kangxi period, he often discussed mathematical problems with mathematicians in China at that time, and Chen Houyao was one of them.

Chen Houyao, a native of Taizhou, Jiangsu Province, was born in 1648. 1706 Jinshi. Because he was familiar with the calendar, Minister Li Guangdi recommended him to Emperor Kangxi and was summoned by Kangxi. Chen Houyao 1708 went to Beijing to be an official. He was a first-rate mathematician at that time and worked as an editor and secretary of imperial academy. Emperor Kangxi deeply appreciated Chen Houyao's mathematical achievements, which was recorded in Historical Records. During the reign of Kangxi in Shunzhi, there was a mathematician named Mei Wending, and his Sun Meixuan was also a famous mathematician during the reign of Kangxi. On one occasion, Kangxi pointed to Chen Houyao and told Mei Juecheng that your grandfather (Mei Wending) is his teacher, but if your grandfather is still alive today, you may have to ask him questions, which shows that Chen Houyao's achievements have surpassed his predecessors, which also reflects Kangxi's profound knowledge of mathematics.

It is also recorded in the history books that when Emperor Kangxi was in power, he often asked foreigners who knew mathematics to tell him about western mathematics. One of the two people who accompanied Kangxi at that time was Chen Houyao.

There is another example of Kangxi's love of mathematics. At that time, many mathematicians gathered in Kangxi's court. At the initiative of Kangxi, many mathematicians, led by Chen Houyao and others, compiled the most famous mathematical encyclopedia of the Qing Dynasty, Essentials of Mathematics. The publication of this book set off the climax of China's study of mathematics in Qianlong and Jiaqing years. At that time, almost all mathematicians in China had one copy, which became a classic textbook of mathematics at that time. There is the word "King James" in this book, which shows that this book was compiled by Emperor Kangxi himself.

In Kangxi's activities related to mathematics recorded in historical books, Chen Houyao's name was mentioned many times. By analyzing the close relationship between them, it is likely that the Pythagorean Diagram was written by Kangxi and Chen Houyao.

In the history of China, few emperors took the initiative to study mathematics, let alone write books. Judging from the research on the history of mathematics so far, Kangxi is the only emperor in China who left behind mathematical works. At present, there is a book on Triangle written by Kangxi in Beijing Library, which is marked with the word "Imperial Compilation", indicating that Kangxi personally participated in the editing of this book at that time. The book Qin Shou by Kangxi, which has attracted much attention, is the second Kangxi mathematics book discovered so far.