Xu Guangqi’s Preface

The Jihe Yuanben can be called the pleasure-garden of the myriad forms, the Erudite Ocean of the Hundred Schools.

Book 1, Def 1.

A point is that which has no part.

Book 1, Def 2

A line is a breadthless lenght

I.47

In right-angled triangles the square on the side subtending the right angle is equal to the squares on the sides containing the right angle.

IV.11

In a given circle to inscribe an equilateral and equiangular pentagon.

E α ?