Japanese Temple Mathematics
In 1627, Yoshida Mitsuyoshi published Jinkō-ki or Large and Small Numbers, one of the earliest computation manuals in Japan and often employed the use of a soroban or abacus. Rather than being for the elite or monks, now the urban population (peasants, merchants, and artisans) could use computations to aid in their daily activities. It became handed down generations as a household reference.
For the remainder of the Edo Period (-1861), temples and shrines were found to have mathematical challenge problems, called sangaku, carved in wood and hung up to encourage others to solve them.
The prompt refers the right-most figure. D is the distance from the upper and lower vertices to the sides of the square that the rhombus is inscribed in, and requires a value of pi to find the solution.
A common misconception is that math is solely the creation of highly-educated European men. This is (1) boring and (2) wrong. As we've seen, a single geometric figure has been contributed to by many cultures and for different reasons (trades computations vs art) because the world we live in will always have different perspectives. Discourse is actually favored in mathematical communities as it brings out the truth, so the more difference, the better.
