“证明题”是中学数学习题中的一个重要组成部分。由于对某些概念理解上的模糊,命题改写以后破坏了与原命题的等效性,或者在论证过程中论据不足、逻辑混乱,这些都容易导致证题不严密的现象,而且证题者往往不知其错误所在。所以对“证题严密性”这个问题进行讨论是十分必要的。下面以命题“求证两两相交而不过同一点的四条直线必在同一个平面内”为例进行分析。一、命题的改写文字证明题常常用数学表达式来改写原命题的条件和结论,使证明的目标具体化。但是改写应在明确 “Proof” is an important part of secondary school math problems. Due to the obscure understanding of certain concepts, the rewriting of the propositions destroys the equivalence with the original propositions or the arguments are not sufficient and the logic is chaotic in the process of argumentation, which can easily lead to the phenomenon of not being rigorous, I do not know where the error. Therefore, it is very necessary to discuss the issue of “Tightness of Tort Questions.” The following proposition, “verify the intersection of two, but the same point of the four lines will be in the same plane” as an example for analysis. First, the rewriting of propositions Proof of writing often use mathematical expressions to rewrite the conditions and conclusions of the original proposition, so that the specific objectives of the proof. But the rewriting should be clear