解答梯形的有关题目时,通常所采取的策略是先把梯形转化为三角形和平行四边形,然后用三角形和平行四边形中的有关知识把问题解决．在此过程中,如何添加适当的辅助线把梯形转化为三角形和平行四边形是解题的关键．下面就梯形中辅助线的常见添加方法举例说明,希望对同学们有所帮助． When answering trapezoidal questions, the usual strategy is to convert the trapezoids to triangles and parallelograms, and then use the relevant knowledge in triangles and parallelograms to solve the problem. In this process, how to add appropriate auxiliary lines to transform trapezoids into triangles and parallelograms is the key to solve the problem. Here is an example of common additions to the auxiliary line in the trapezium. I hope to help the students.