一、三角函数在平面几何中的应用某些平面几何题,线段与线段、角与角、线段与角的关系比较复杂,单纯采用平面几何的知识进行证明.有时不易找到证明题的途径,如改用三角法来证,不仅证题过程简捷,而且证题的思路也比较自然,易于达到证明题的目的.用三角法来证明关键是把几何 First, the application of trigonometric functions in plane geometry Some of the plane geometry, line and line segments, angle and angle, the relationship between the line segment and angle is more complex, simply using the knowledge of plane geometry to prove that sometimes difficult to find ways to prove the title, such as Use trigonometry to prove that not only the process of the title is simple, but also the idea of ​​the title is more natural and easy to achieve the purpose of proving the problem.Using trigonometry to prove that the key is the geometry