梯形是一类应用广泛的特殊四边形,虽然课本(人教社九年义务教育初级中学教科书《几何》第二册,下同)上讲述它的内容不多,但它在几何中的位置却举足轻重.学好梯形知识,既是巩固三角形,平行四边形知识的途径之一,又是继续学习平几和立几内容的必须.准确、迅速的解证梯形题是学好梯形知识的标志.解证梯形题时,大多要添加辅助线,将问题给予转化.所以,掌握常见的添辅助线方法,对发掘条件与结论之间的联系,寻找解题路径至关重要,解证梯形题常见的添辅助线方法,课本上大多已给出,为了条理和系统,这里简略归纳如下,供同行参 The trapezoid is a type of special quadrilateral that is widely used. Although the text is not much described in the textbook (the second edition of the textbook for the junior high school of the People’s Education Association’s nine-year compulsory education, the same below), its position in the geometry plays a decisive role. Learning trapezoidal knowledge is not only one of the ways to consolidate the knowledge of triangles and parallelograms, but also the necessity of continuing to learn the contents of peace and stability. Accurate and rapid solution to trapezoidal problems is a sign to learn trapezoidal knowledge. When solving trapezoidal problems, Most of them need to add auxiliary lines to transform the problem. Therefore, it is very important to master the common method of adding auxiliary lines, to explore the connection between conditions and conclusions, and to find the solution path. Most of the textbooks have been given. For the sake of organization and system, here are briefly summarized as follows: