题目

Betty is an English girl. She is twelve years old. Her QQ number is 68971520. Betty likes football. The colour of her football is black and white, Tony is Betty's friend. He is a nice boy. He is twelve years old too. Tony's favourite sport is table tennis, He likes playing table tennis on Saturday. Betty and Tony are in Class 5. There are 23 boys and 27girls in this class, Miss Wang is their Chinese teacher. She likes reading books to her students. Today is Friday and the weather is warm. Betty and Tony are playing football on the playground. They are very happy. 【1】What colour is Betty's 16．如图，在△ABC中，已知AB=AC=3，BC=4，且△ABC≌△DEF，将△DEF与△ABC重合在一起，△ABC不动，△DEF运动，并满足：点E在边BC上沿B到C的方向运动，且DE始终经过点A，EF交于AC于M点．（1）求证：△ABE∽△ECM；（2）探究：在△DEF运动过程中，△DEF与△ABC的重叠部分能否构成等腰三角形？若能，求出BE的长；若不能，请说明理由．