求证：△ABE≌△CDF．

完形填空

      Hey, I'm Simon. I have a strong and faithful dog, Bruce. The dog likes1with me. Sometimes he also follows my father to work. One morning when my father worked in the field, he2 his coat and put it under a big tree. He turned  to the dog and said,“3my coat, Bruce!” Bruce sat down on the coat. Later, my father remembered he had to buy some food.  4 he hurried to the shop.   5 shopping, he went home directly and forgot completely about his 6 and the dog. In the evening, I looked for my dog7 in the house, but I8 find him. At this time, my father suddenly remembered his coat and the dog. He went back to the tree   9. He found that Bruce was 10 sitting on the coat!

如图，测量人员在山脚A处测得山顶B的仰角为45°，沿着仰角为30°的山坡前进1000米到达D处，在D处测得山顶B的仰角为60°，求山的高度？