**Choi Seok-jeong** was a Korean politician and mathematician who was the first to find orthogonal Latin squares. He constructed magic squares and invented the Hexagonal Tortoise Problem.

- At this time Choi Myeong-gil was Jwauijeong, the Second State Councillor of the Uijeongbu (State Council), and he went to Shenyang in China in 1637 to negotiate the release and repatriation of Korean prisoners of war.
- By the age of 9, Choi Seok-jeong had already memorised the Book of Songs, a Chinese Confucian classic collection of poems, and The Book of Records, a history chronicle.
- There are 24 letters written by Choi Seok-jeong to Lee Segu on arithmetic, astronomy, and calendars which reflect their research together.
- Before looking at some of Choi Seok-jeong's major mathematical contributions, let us explain what Latin squares are, what orthogonal Latin squares are, and how magic squares are made from pairs of orthogonal Latin squares.
- This, however, is not the case since an example of two orthogonal Latin squares of order 9 appear in the book "Gusuryak" written by Choi Seok-jeong.
- Asian traditional mathematics was based on the "Nine Chapters on the Mathematical Art." Choi classified mathematical operations, problems and all nine chapters into four classes, represented by the four sasang symbols.
- Choi Seok-jeong comments in "Gusuryak" that he was unable to construct orthogonal Latin squares of order 10.
- It was not only Choi Seok-jeong and Euler who failed to construct orthogonal Latin squares of order 10 for attempts to construct such a square became an obsession for many mathematicians over the years.
- There is another fascinating problem invented by Choi Seok-jeong which appears in the "Gusuryak", namely the Hexagonal Tortoise Problem.
- Choi's study of magic squares contained some results never seen in Chinese mathematics, and other results are applicable today to the hexagonal tortoise problem of coding theory.
- After resigning from his government positions, Choi Seok-jeong lived mainly at the foot of Sorae Mountain.
- It is only in recent years that Choi Seok-jeong's contributions to mathematics have been fully recognised.
- Choi Seok-jeong was appointed to the Korea Science & Technology Hall of Fame on 23 November 2013 by the Ministry of Science and Technology and the Korean Academy of Science and Technology.
- On 6 September 2018, a ceremony was held to commemorate the completion of the Choi Seok-jeong seminar room at the Korea Advanced Institute of Science and Technology.

Born 2 July 1646, Chopyeong-myeon, Jincheon-gun, South Korea. Died 6 December 1715, Chopyeong-myeon, Jincheon-gun, South Korea.

View full biography at MacTutor

Origin South Korea

**Oâ€™Connor, John J; Robertson, Edmund F**: MacTutor History of Mathematics Archive