“错位中点”是指不共端点的两条相交线段的中点.由于它有别于我们熟悉的基本图形,所以常常令我们的思路受阻.解决它的关键是将这种非常规图形转化为我们熟悉的基本图形,从而建模求解.下面通过一道习题介绍解决这类问题的一般思路和方法.题目如图1,已知四边形ABCD的对角线AC与BD相交于点O,且AC=BD,M、N分别是AB、CD的中点,MN分别交BD、AC于点 “Dislocation midpoint ” refers to the midpoints of two intersecting line segments that are not altogether in the endpoints, and because it is different from the familiar basic graphics, it often hinders our thinking. The key to solving this problem is to take this unconventional Graphics into familiar with the basic graphics, modeling solutions.Through an exercise to introduce the general ideas and methods to solve such problems.The subject is shown in Figure 1, known quadrilateral ABCD diagonal AC and BD intersect at point O, And AC = BD, M, N are the midpoints of AB and CD, respectively, and BD are respectively given BD and AC at points