问题背景:期末试卷,有一道题做对的学生极少.这道题真的很难吗?原题:如图1,半圆的直径AB=5,弦AC=3,将半圆沿着AD折叠后弦AC恰好落在AB上,则折痕AD的长为____.显然,不添辅助线难以得出答案.因为求线段的长度要利用等腰三角形、直角三角形或相似等方法.题目中显然都不具备,所以要添辅助线,怎样添辅助线,不同的学生从题目中获知的信息不同,因而所添 The problem is: the final papers, there is a problem to do very few students. Is this really difficult? Original title: Figure 1, the diameter of the semicircle AB = 5, chord AC = 3, the semicircle along the AD fold Obviously, it is hard to get the answer without adding the auxiliary line because the length of the line segment needs to use isosceles triangle, right triangle or the like method. Obviously do not have, so to add auxiliary line, how to add auxiliary line, different students learn from the title of the different information, which Tim