在平面几何中 ,我们曾经研究过两个图形相似问题 ,如两三角形相似问题 .由两图形相似的概念(见文 1)可知任意两圆是相似图形 .下面叙述一个事实 :任意两抛物线是相似图形 .图 1　抛物线尽管三条抛物线c1:y2=8x ,c2 :y2 =4x ,c3:y2 =2x(如图 1)给我们有开口宽窄的感觉 ,但从以下 In plane geometry, we have studied two graph similar problems, such as two triangles similarity problem. From the concept of two similar graphs (see article 1) we can see that any two circles are similar graphs. Here is a description of the fact that any two parabolas are similar. Figure 1. Figure 1 Parabola Although the three parabola c1:y2=8x, c2:y2=4x, c3:y2=2x (Figure 1) gives us the feeling of opening width, but from below