This is a page from the below book, Sacred Mathematics: Japanese Sacred Geometry. The problems described in the sangaku are quite unique. Sangaku flourished during the Edo period. Due to Japan’s isolationist policy (Sakoku), under which no foreigner could enter the country, Japan was without any knowledge of the developments of calculus in Europe. Most Westerners, then and now, would see these problems as exercises requiring calculus; yet the Japanese developed their own methods for solving their problems. This sangaku looks at determining the surface area of a globe by determining the surface area of the smaller globes surrounding it.