关键词: 角度, 平面角, 分类, 探讨

Abstract: The frequently used angle was the plane angle in the International System of Units, so the starting point of classification should be the plane performance of the plane angle. Because of the plane was divided into geometric plane and physical plane, so the plane angle could be divided into two parts: geometric angle and physical angle. The geometric angle was divided into arbitrary angle (circle indexing angle), fixed angle and small angle; the physical angle was divided into projection angle on horizontal plane, projection angle on vertical plane and projection angle on specific plane. The new classification method was proposed just as suggestion for discussions.

Key words: Angle, Plane angle, Classification, Discussio