梯形中隐含着一些基本图形,如直角三角形、矩形、全等三角形、相似三角形、平行四边形等。有关梯形问题作辅助线是为了把这些隐含的基本图形显示出来,以便运用相关的几何性质,达到证题或解题的目的。 一般梯形问题,常作的基本辅助线有以下几种: (1)由梯形的小底两端作大底的垂线; (2)由小底的一端作一腰的平行线,或作另一对角 Trapezoids contain some basic graphics, such as right triangles, rectangles, congruent triangles, similar triangles, parallelograms, and so on. The auxiliary line for the trapezoidal problem is to display these hidden basic figures so that the relevant geometrical properties can be used to achieve the purpose of proof or problem solving. In general trapezoidal problems, the basic auxiliary lines often used are the following: (1) The vertical line at the bottom of the small base of the trapezoid is the vertical line at the big bottom; (2) The parallel line at the bottom of the small base is a waist, or for another One corner