Born in a samurai familly in feudal Japan, I started completing a samurai education...but switched at age 13 with my brother to study mathematics under the brilliant Seki Takakazu.
At this time, the mathematicians in Japan were of the wasan (“Japanese calculation”) tradition...we were unaware of nonJapanese mathematics, thus limiting us to using sticks in lieu of numbers...and the ideas of trigonometry were unheard of.
Working with Seki, we tried to build a new mathematical science in Japan, developing algebra and analysis.
I had a special interest in Pi, once using Archimedes' exhaustion techniques on a polygon with 1024 sides to calculate Pi accurately to 41 decimal places.
My greatest achievement was devising a method for calculating a series expansion of what basically was a function.
In my Classique, I used the expansion technique to be the first to express the square of a circle arc in the from of an inifite sum, which led to a numerical algorithm for generating Pi slowly.
Answer:
Takebe Katahiro (1664 — 1739)
