题目

Have you ever stayed in a hotel? Most Chinese hotels often provide guests with things like disposable (一次性的) toothbrushes, toothpaste, shampoo and slippers. Many guests like the idea because they don't have to bring their own. But, if you travel to Beijing, remember to bring your own things. Starting from June, some hotels in Beijing will no longer provide guests with these disposables. They want to ask people to use less disposable things. Many disposable things are made of plastic. People throw them away after only using them once. It is a waste of natural resources (资源) and 已知：如图，AD是△ABC的高，AB=AC，BE=2AE，点N是CE的中点．求证：M是AD的中点．