梯形是在三角形和平行四边形的知识基础上进行研究的．因此，我们在研究梯形问题时，常需要先添加适当的辅助线，把梯形问题转化成三角形或平行四边形问题，然后应用三角形或平行四边形的有关知识来解决梯形问题．笔者在此谈谈解决梯形问题时添加辅助线的方法，希望能对同学们 The trapezoid is studied based on the knowledge of triangles and parallelograms. Therefore, when we study the trapezoidal problem, we often need to add appropriate auxiliary lines, convert the trapezoidal problem into a triangle or parallelogram problem, and then apply the relevant knowledge of triangles or parallelograms to solve the trapezoidal problem. The author here talks about the method of adding auxiliary lines when solving the trapezoidal problem, hoping to be able to deal with the students