During this period Japan applied strict regulations to commerce and foreign relations for western countries so the tablets were created using Japanese mathematics, (wasan), developed in parallel to western mathematics. For example, the fundamental connection between an integral and its derivative was unknown, so Sangaku problems on areas and volumes were solved by expansions in infinite series and term-by-term calculation.
A typical problem, which is presented on an 1824 tablet in the Gunma Prefecture, covers the relationship of three touching circles with a common tangent. Given the size of the two outer large circles, what is the size of the small circle between then?
Fujita Kagen (1765–1821), a Japanese mathematician of prominence, published the first collection of sangaku problems, his Shimpeki Sampo (Mathematical problems Suspended from the Temple) in 1790, and in 1806 a sequel, the Zoku Shimpeki Sampo.
http://en.wikipedia.org/wiki/Sangaku