八年级是同学们学习平面几何的关键时期,尤其是《平行四边形》一章的学习,综合性强.下面,仅就一题目加以分析,希望能开阔同学们求解此类几何题的思路.已知:△ABC的两条高BD,CE交于点F,点M,N分别是AF,BC的中点,连接ED、MN.(1)在图1中证明MN垂直平分ED;(2)当∠BAC=45°时(如图2),判断以M,E,N,D为顶点的四边形的形状,并证明你 The eighth grade is a crucial period for students to study plane geometry, especially the study of “Parallelogram”, which is comprehensive and comprehensive.After that, we only analyze one subject and hope to broaden the train of thought for students to solve such geometry problems. Know: △ ABC two high BD, CE to point F, point M, N are the midpoint of AF, BC, ED, MN. (1) When ∠BAC = 45 ° (Figure 2), judge the shape of the quadrilateral with M, E, N, D as the vertices and prove that you