Sangakus

Plate 2.1. This illustration of a man mea sur ing the height of a tree using basic trigonometry is from an edition of the JinkoÂŻ- ki published between 1818 and 1829, but, like most of the problems in the JinkoÂŻ- ki, it was passed down from Chinese sources.

The problem asks for two ways a woodsman can use trigonometry and/or a stick of known length to mea sure the height of a tree. Compare problem 2- 3 in this chapter.

(Collection of Fukagawa Hidetoshi.)