【片断回放】教学“梯形的面积”一课时,在学生推导出梯形的面积计算公式,并利用公式进行基本计算之后,出示了下题(课本中的练习题):观察下面的梯形,你发现了什么?通过计算、观察和讨论,学生很快发现了上面“三个梯形上下底的和相等,高也相等,虽然形状不同,但是它们的面积一定相等”。这时,我进一步追问:“如果面积和高都不变,它的上、下底还可能分别是几厘米?你能再画出几个这样的图形吗?完成之后小组 When the student deduces the calculation formula of trapezoid and formulates the basic calculation, he presents the following question (Exercises in the textbook): When observing the following trapezoid, What did you find out? Through the calculation, observation and discussion, the students soon discovered that ”the top and bottom of the three trapezoids are equal in height and equal in height, although their shapes are different, but their areas must be equal.“ At this moment, I further question: ”If the area and high are the same, its upper and lower base may also be a few centimeters respectively? Can you draw a few more such graphics? After the completion of the group