为了证明的需要 ,在原来的图形上添画的线叫做辅助线 ,添辅助线是解决几何问题不可缺少的重要手段 .而利用定义巧添辅助线就是当几何问题中的条件或结论中出现直接和某一基本概念有关的性质 (如线段或角的和差倍分问题等 )时 ,就可以根据这些要领的定义添加辅助线 下面举例说 In order to prove the need, the lines added on the original graphics are called auxiliary lines. Adding auxiliary lines is an indispensable means to solve geometric problems. Using the definition to add auxiliary lines is a direct result of the conditions or conclusions in the geometric problem. When related to a basic concept (such as the segment or angle and differential multiples, etc.), it is possible to add auxiliary lines based on the definitions of these guidelines.