关于平面射影几何中同素变换下的不变元素的注记

The Note on the Stable Elements of the Same Elements Change in Projective Geometry of Plane

射影平面上的变换包括同素变换和异素变换.同素变换下保持不变的点称为不变点,保持不变的线称为不变直线.两个不变点的连线一定是不变直线,两条不变直线的交点一定是不变点.

The transformation on the projective plane include the same elements change and the unlike elements change.The former is made up of invariant points and invariant lines.The line of the two invariant points must be a invariant line,the crossover point of the two invariant lines must be a invariant point.