What Are Sangaku?
Sangaku are Japanese votive mathematical tablets containing geometrical and/or landscape problems. They first appeared during the Edo period (1603-1868 CE) and continued to be created throughout the nation until the late Meiji period (1868-1912 CE). In modern times, there has been a revival in the tradition and many new tablets are being created.
The term Sangaku is made of san 算 – which means calculation – and gaku 額 – which means plaque. These tablets were made from solid wood, and came in a variety of sizes. On average they ranged from a width of 153 cm and height of 69.4 cm. Sangaku were traditionally placed in Shinto shrines and Buddhist temples. Many are still in their original locations and can be viewed today (see the locations page).
Sangaku usually presented their problems in three different sections:
- Problem: Introductory section describing the diagram and indicating which figure from the diagram the observer needs to find the value of.
- Answer: Section giving either the numerical value of the sought figure or advising to refer to the next section.
- Procedure: Section which provided a formula for obtaining the solution.
While sangaku usually provided a formula for finding the solution, they did not provide any working, leaving the observer to find the solution on their own.