在教学“周期问题”中的排列规律时,如果讲解的方法太多反而会让学生思路不清晰,容易产生混乱。本文力图从精准的角度帮助学生整理这一问题,使之思路清晰,理解到位。 In the teaching “cycle problem ” in the arrangement of law, if too many ways to explain but will make students not clear idea, prone to confusion. This article tries hard to help the students organize the problem from a precise point of view, to make their thinking clear and understand the place.