对于一个命题,当使用直接证法比较困难时,可以采取间接证法,“反证法”就是一个间接证法.在讲解这一部分内容时,学生感到最困难的地方应该是在分析“由假设出发,经过推理论证得出矛盾”中如何进行严密的推理,并真正理解矛盾在哪里.教学时如何帮助学生克服这个难点呢?这里,笔者谈两点体会. For a proposition, when using the direct method is more difficult, you can take the indirect method, “reverse method ” is an indirect method, in explaining this part of the content, students feel the most difficult place should be in the analysis Hypothesis Departure, Obtaining Contradictions through Reasoning Argument, "and how to make a rigorous reasoning and really understand where contradictions are. How can teaching help students to overcome this difficulty? Here, I will talk about two points.