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在中考试题中有一类“动点经过的路径计算”的问题,从学生的解答来看,由于思考的切入点不当,得分比较低,教学中有必要给予应有的关注.本文以几个典型案例对这类问题进行探讨.1画图定路径有的题目正确画出路径是求路径长的关键.例1如图1,等腰梯形MNPQ的上底长为2,腰长为3,一个底角为60°.正方形ABCD的边长为1,它的一边AD在MN上,且顶点A与M重合.现将正方形ABCD在梯形的外面沿边MN、NP、PQ进行翻滚,翻滚到有一个顶点与Q重合即停止滚动.
In the middle school exam questions there is a class of “path calculation”, from the student’s point of view, due to improper starting point for thinking, the score is relatively low, it is necessary to give due attention in teaching.This article in a few A typical case of such issues to be discussed.1 Draw a path and some problems Correct drawing of the path is to find the key to the path length.Example 1 As shown in Figure 1, isosceles trapezoid MNPQ on the bottom length of 2, the waist length of 3, A base angle is 60. The square ABCD has a side length of 1, one side of which AD is on MN, and the vertex A coincides with M. The square ABCD is now tumbled outside the trapezoid along edges MN, NP, PQ, tumbling to A vertex coincides with Q and stops scrolling.