人民教育出版社出版的高中数学高级中学课本《平面解析几何》全一册 (必修 ) (以下简称课本 )第 78页 ,是这样引入椭圆第二定义的 :图 2 -18“例 3　点Ｍ(ｘ ,ｙ)与定点Ｆ(ｃ,ｏ)的距离和它到定直线Ｌ:ｘ =ａ2ｃ 的距离的比是常数ｃａ(ａ ｃ0 ) .求点Ｍ的轨迹 (图 2 -1 8) .? High school mathematics high school textbooks published in the People’s Education Publishing House, “Plane Analytical Geometry,” a book (required) (hereinafter referred to as textbooks) on page 78, is the second definition of the introduction of the ellipse: Figure 2-18 "Example 3 points M ( The ratio of x, y) to the fixed point F(c, o) and its distance from the fixed line L:x = a2c is a constant ca(a c0) . The trajectory of the point M (Figure 2 - 1 8) .?