角是众多几何图形的基本组成元素,如何研究角也相应成为几何中的一个基本问题.纵观学生对角的认识发展历程,从小学由现实生活观察发现角、用量角器度量感知角,到初中在直角三角形中,初步引入三角函数研究特殊角,再到高中在直角坐标系中拓展到用三角函数研究任意角,实现了“由特殊到一般”、“从有限到无限”质的飞跃。我们知道三角函数的本质是任意角的集合与比值的集合之 Angle is the basic composition of many geometric elements, how to study the angle has become a corresponding geometric problem in a fundamental view of the development of students diagonal understanding of history, from primary school observation angle found in real life, the angle of measurement of perceived angle, to junior high school In trigonometric triangles, trigonometric functions are introduced initially to study special angles, and then to high school, which is extended to study arbitrary angles by trigonometrical functions in Cartesian coordinates, thus achieving a “from special to general” and “finite to infinite” qualities Leap. We know that the essence of trigonometry is the collection of arbitrary angles and the set of ratios