有关抛物线切线与焦点的一些性质

Some Properties of Parabola Tangent and Focus

在二次曲线的研究中,射影几何方法给出了二次曲线的一些有趣的性质。用射影几何研究平面几何就是把讨论的对象放在拓广平面上,用射影几何知识进行研究。本文将二次曲线中的抛物线放在拓广平面上,用射影几何的方法进行研究,并给出了有关抛物线切线与焦点的一些性质,特别是由抛物线切线与焦点得到的相似三角形的性质。

In the study of the quadratic curve,the method of projective geometry provides quadratic curve some interesting natures. To study plane geometry by using projective geometry is to set the object discussed on extension of the parabolic surface,then study it with the knowledge of projective geometry. This paper sets parabola of the quadratic curve on extension of the parabolic surface and studies it with projective geometry,and gives some properties of parabola tangent and focus,especially the properties of similar triangle obtained by parabola tangent and focus.