教科书在每一章的开头都有一段话──章引言;有的还配有与本章内容配套的图片——章头图.章引言通常是对本章所涉及到的内容、思想方法做一个简要的介绍,章头图往往是展示本章内容在科学技术中的应用,传播数学文化等.比如,圆锥曲线这一章的章头图展示了圆锥曲线性质的应用──雷达的抛物线天线、人造卫星运行的轨道画面等等.但是,在教学中,往往对 Textbooks have a paragraph at the beginning of each chapter—chapter introduction; some also have pictures matching the contents of this chapter—chapter head pictures. Chapter introductions are usually a brief introduction to the content, ideas and methods involved in this chapter. In the introduction, the chapter head diagram often shows the application of this chapter in science and technology, and spreads the mathematics culture. For example, the chapter head of the conic section shows the application of the conic curve: Radar Parabolic Antenna, Satellite Run the track screen and so on. However, in teaching, often