was a Japanese

mathematician A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, structure, space, models, and change. History On ...

of the

Edo period The or is the period between 1603 and 1867 in the history of Japan, when Japan was under the rule of the Tokugawa shogunate and the country's 300 regional '' daimyo''. Emerging from the chaos of the Sengoku period, the Edo period was characteriz ...

. He was the lord of

Kurume Domain was a Japanese domain of the Edo period. It was associated with Chikugo Province in modern-day Fukuoka Prefecture on the island of Kyushu. In the han system, Kurume was a political and economic abstraction based on periodic cadastral surveys a ...

. He approximated the value of

\pi

and its

square In Euclidean geometry, a square is a regular quadrilateral, which means that it has four equal sides and four equal angles (90-degree angles, π/2 radian angles, or right angles). It can also be defined as a rectangle with two equal-length adj ...

\pi^2

. In 1766, he found the following rational approximation of

\pi

, correct to 29 digits: :

\pi\approx\frac=3.14159265358979323846264338327(569...).

References

Further reading