Use rotation skillfully to reduce the elements
巧用旋转，化归元素

摘要

近年来，图形的旋转变换已成为中考试题的热点之一，几何问题题目中虽没有“旋转”二字，解题思路常需要构造旋转化归元素，即将元素集中或分散，从而巧妙解决较难的几何问题，考验学生的几何直观和空间想象能力。应用“图形的旋转”对几何图形运动问题展开研究，把静止的问题转化成动态，可以拓展学生的想象空间，挖掘知识间的内在联系，构造出新的图形[1]。因此，教师应在本单元教学时多挖掘学生的动态思维过程。几何问题变换虽然难度较大，若能针对题目的本质特征，合理的运用旋转，往往可以化难为易，化繁为简[2]。

Abstract

In recent years, the rotation transformation of graphics has become one of the hot topics in the middle school exam. Although there is no word “rotation” in the geometry problem, the solution idea often needs to construct the rotation to reduce the elements, that is, the element is concentrated or dispersed, so as to solve the difficult geometric problems skillfully, and test the students' geometric intuition and spatial imagination ability. The application of “rotation of graphics” to the study of the motion of geometric figures, the transformation of static problems into dynamic problems, can expand students' imagination space, excavate the internal relations between knowledge, and construct new graphics. Therefore, teachers should explore students' dynamic thinking process in the teaching of this unit. Although the transformation of geometric problems is difficult, if we can reasonably use rotation according to the essential characteristics of the problem, we can often transform the difficult into easy and complex into simple.