在初中数学中,有一类所谓的条件变化探索题.其特点是,在已知条件下,先证明或确定一个结论,然后将题目条件变化,要求探索原来的结论是否仍然成立.解答它们,有时需要灵活应用图形全等的知识.下面举例说明,供参考.例1在△ABC和△ADE中,AB=AC,AD=AE,∠BAC=∠DAE=90°.(1)当点D在AC上时,如图1所示,线段BD,CE有怎样的数量关系和位置关系? In junior high school mathematics, there is a class of so-called conditions of change exploration questions, which is characterized by known conditions, the first to prove or determine a conclusion, and then change the conditions of the topic, to explore whether the original conclusion is still established to answer them, sometimes Example 1 In △ ABC and △ ADE, AB = AC, AD = AE, ∠ BAC = ∠DAE = 90 ° (1) When the point D is at AC, as shown in Figure 1, the line segment BD, CE, what is the relationship between the number and location?