Since there was no 360°central angle system in ancient China, how did the ancient people express the concept of angle when coming to them? The answer can be found in Kao Gong Ji. Through detailed studies we find there were already some proper~stood for abstract concept of angles and some specific angles used as technical standards in Kao Gong Ji. These angles were constructed by performing geometric operations on the basic angle Gui or Ju. What is called the contradiction of Jugou Qingzhe does not exist.
On the Concept of Angle in Kao Gong Ji