Arima Yoriyuki
An 18th-century Japanese feudal lord who applied his mathematical genius to calculate pi with astonishing accuracy using traditional wasan methods.
1714–1783 (age 69)·Japanese mathematician·Birthday: December 31
Biography
Arima Yoriyuki was a daimyo, a lord governing the Kurume Domain, who presided over his lands with the same intellectual rigor he applied to his private passion: mathematics. In the Edo period tradition of wasan, or Japanese calculation, scholars pursued math as an art form. Yoriyuki's masterpiece was a monumental calculation of the circle constant pi. Using a painstaking geometric method of inscribing polygons within a circle—a technique echoing Archimedes but developed independently—he arrived at a value correct to 29 decimal places. This feat, detailed in his work "Shuki Sanpo," was a towering achievement of pre-modern computation. Yoriyuki embodied the scholar-lord ideal, demonstrating that administrative duty and profound scholarly pursuit could coexist, leaving a permanent mark on the history of mathematics from his remote island nation.
#1 When Arima Was Born
The biggest hits of 1714
Arima's Life & Times
The world at every milestone
1714Born
1719Started school
1727Became a teenager
1730Could drive
1732Could vote
1735Turned 21
1744Turned 30
1754Turned 40
1764Turned 50
1774Turned 60
1783Died at 69
Key Achievements
- Calculated the value of pi to 29 decimal places in 1766, a record for wasan mathematics at the time.
- Authored the mathematical text "Shuki Sanpo" which detailed his methods for calculating pi and other problems.
- Served as the 8th lord of the Kurume Domain, successfully managing its political and economic affairs.
Did You Know?
His calculation of pi used a 2^30-sided polygon (over one billion sides in theory).
He was a student of the famous wasan mathematician Yamaji Nushizumi.
Despite his high social status, he deeply engaged in the collaborative, problem-solving culture of wasan circles.
“Numbers reveal the true pattern of the heavens and the earth.”
