张景中/主编本书从小学生知道的三角形内角和的知识以及三角形面积公式出发,举一反三,推陈出新,直观而严谨地给出正弦的新定义。在此基础上,轻松得到正弦定理、和角公式、勾股定理等一系列三角公式和几何定理,揭示出几何、代数和三角的基本知识之间的密切联系,以三角为主线,构建了初等数学的新体系。书中思想新颖,方法简明犀利,说理严谨,特别着力于从平凡处发掘创新的思路,引导读者发现问题,深入思考。 Zhang Jingzhong / editor in chief of the book from the pupils know the triangle angle and knowledge and the triangle area formula starting from the world, innovation, intuitive and rigorous given a new definition of sine. On this basis, a series of trigonometric formulas and geometric theorems such as sine, angle, pythagorean theorem and so on are easily obtained, which reveal the close relationship between the basic knowledge of geometry, algebra and trigonometry. New mathematical system. The book novel thinking, the method is concise and sharp, rigorous rigor, with particular emphasis on exploring innovative ideas from the ordinary, to guide readers to discover problems, in-depth thinking.