例1如图1,点D在AB上,点E在AC上,AB=AC,∠B=∠C.求证AD=AE.例2如图1,AB=AC,AD=AE.求证∠B=∠C.上两题分别是人教版《数学》(八年级上册)中第40页和第43页的题目.两题互换了结论和部分条件,可称之为“姊妹题”.题中的图形属于全等三角形的一种基本类型——“对称型”(关于过点A,O的直线对称),可看作是把等腰 Example 1 As shown in Figure 1, point D is on AB, point E is on AC, AB = AC, ∠B = ∠C. Verification AD = AE. Example 2 In Figure 1, AB = AC, AD = AE. = ∠ C. The two questions are the PEP (Mathematics) (eighth grade) on page 40 and page 43. The two questions exchange the conclusion and some of the conditions, which can be called “sister problem The graphic in question is one of the basic types of congruent triangles - ”Symmetry " (on the line symmetry of point A, O), which can be considered as isosceles