关于笛沙格定理的附注

A Note on Desargues Theorem

笛沙格定理在平面射影几何中必须选作公理,然而一般的高等几何教科书又都用投到无穷远法或解析法对它加以证明,本文从几何基础的角度指出了这种处理的合理性。

In plane projective geometry, Desargues theorem is always chosen as an axiom. Nevertheless, it can be proved by using the method of infinite proje-ctivity, or by analysis as shown in ordinary higher geometry textbooks. This paper makes an analysis and indicates that, from geometrical foundation's point of view the usual treatment is reasonable.