Abstract
Once I saw a handout which was used at a secondary school in 1945, where the real shape of the cross section of a cone was asked The handout contains the projection chart of a cone and a plane, which means the space geometry and the descriptive geometry were tightly connected in math classes at that time. From the Meiji era, they were taught separately in mathematics and drawing. Under the 1942/43 syllabi, descriptive geometry was widely adopted in "Daini-rui" (the 2nd part) of mathematics course. Through the handout and real notebooks at that time, I found that the projection skills were actively used in the study of conic sections. Although the projection was left in the mathematics in middle schools for a while in the post war secondary school system, useful contents were very much limited such as real length of a segment. Finally, descriptive geometry was completely deleted from secondary school mathematics when the course of study was revised in 1969. It is important to investigate the relationship between space geometry and descriptive geometry, and use the latter effectively to teach the former.
