题目

If you can read a clock, you can know the time of the day. But no one knows what time itself is. One way to think about time is to imagine a world without time. But there could be no movement, because time and movement cannot be separated. In early human history, the only changes that seemed to repeat themselves evenly were the movements of objects in the sky. The most easily seen result of these movements was the difference between light and darkness. The sun rises in the eastern sky, producing light. It moves across the sky and sinks in the west, causing darkness. The appearance and为了测量两山顶M，N间的距离，飞机沿水平方向在A，B两点进行测量，A，B，M，N在同一个铅垂平面内（如示意图），飞机能够测量的数据有俯角和A，B间的距离，请设计一个方案，包括：①指出需要测量的数据（用字母表示，并在图中标出）；②用文字和公式写出计算M，N间的距离的步骤。