一、知识要点1．利用正弦定理和余弦定理．可实现三角形边、角关系之间的互相转化，从而为解决有关问题提供条件．2．利用正、余弦定理可解决多边形和圆等图形中的计算问题以及生产实践中的某些实际问题．在此，关键是将有关问题归结为三角形问题．二、解题指导例1在△ARC中， First, knowledge points 1. Use sine theorem and cosine theorem. The mutual transformation between triangle edges and angles can be realized, thus providing the conditions for solving the problems. 2. The use of positive and cosine theorem can solve the computational problems in polygons and circles and other practical problems in production practice. The key here is to attribute the problem to a triangular problem. Second, problem solving guide example 1 in △ ARC,