在数学学习中,对某些习题进行变化和延伸,这对提高我们的探索能力,解题能力大有裨益.现以九年义务教育教材《几何》第二册习题三A组第13题为例,说明如何对一道习题进行多角度,全方位地变化和延伸,可从中将得到一系列变式训练题(证明过程这里均略). In mathematics learning, changes and extensions are made to certain exercises. This is of great benefit to our ability to explore and to solve problem-solving abilities. Now we have a nine-year compulsory education textbook “Geometry” in the second volume of exercises. Examples show how to perform a variety of angles on an exercise and change and extend it in all directions. A series of variant training questions will be obtained from it (the proof process is omitted here).