Ceyuan haijing.

About Ceyuan haijing

Ceyuan haijing is a treatise on solving geometry problems with the algebra of Tian yuan shu written by the mathematician Li Zhi in 1248 in the time of the Mongol Empire. It is a collection of 692 formulas and 170 problems, all derived from the same master diagram of a "round town" inscribed in a right triangle and a square. They often involve two people who walk on straight lines until they can see each other, meet or reach a tree or pagoda in a certain spot.