解析几何课本P101页,有这样一道: 题目经过抛物线y2=2px的焦点F,作一条直线垂直于它的对称轴,和抛物线相交于A、B两点,线段AB叫做抛物线的通径.求通径AB的长. 解此题可用两种方法解法一(用定义): 如图1,过A、B作准线L的垂线,垂足是D、C, Analytic geometry textbook P101 page, there is such a: The topic through the parabolic y2 = 2px focus F, as a straight line perpendicular to its axis of symmetry, and the parabola intersect in two points A, B, line AB called the parabolic path. The length of the path AB. There are two ways to solve this problem. Solution one (with the definition): As shown in Figure 1, the vertical lines passing through A and B are the vertical lines of L. The feet are D and C.