High Quality Content by WIKIPEDIA articles! Sangaku or San Gaku are Japanese geometrical puzzles in Euclidean geometry on wooden tablets which had dedicated to Shinto shrine during the Edo period (1603 1867) by members of all social classes. The Sangaku were painted in color on wooden tablets and hunged in the precincts of Buddhist temples and Shinto shrines as offerings to the gods or as challenges to the congregants or publish what question one solved. Many of these tablets were lost during the period of modernization that followed the Edo period, but around nine hundred are known to remain. The Dutch Japanologist Isaac Titsingh first introduced sangaku to the West when he returned to Europe in the late 1790s after more than twenty years in the Far East.