一、试题探源义务教育课程标准实验教科书人教版八年级数学下册P119页练习中第2题是:图1如图1,四边形AB-CD由三个全等的等边三角形组成,它是一个等腰梯形吗?为什么?由题设条件不难判断四边形ABCD为等腰梯形.反思求解过程,可发现此梯形由题设条件有AB=CD=AD,BC=2AD.即梯形的上底与两腰相等,下底等于上底的两倍,且下底角等于60°. First, the source of the test questions Compulsory education curriculum standard experimental textbook PEP eighth grade mathematics volume P119 page exercises in the second question is: Figure 1 Figure 1, quadrilateral AB-CD consists of three congruent equilateral triangles, it Is it an isosceles trapezoid? Why? It is not difficult to judge by the conditions of the quadrilateral ABCD isosceles trapezoid. Reflections on the process of solving this trapezoid can be found by the conditions set AB = CD = AD, BC = 2AD. Bottom and two lumbar equal, bottom equal to twice the upper base, and lower base angle equal to 60 °.