反证法就是通过论证与原命题相矛盾的命题为假，从而肯定原命题是正确的证明方法．不少数学命题的证明，当使用直接证法比较麻烦或比较困难甚至不可能时，如能恰当使用反证法，往往可以有较好的效果．反证法证明的一般步骤为：①反设．假设原命题的结论不成立，即与其相矛盾的 Defeating the law is to prove that the original proposition is the correct proof by arguing that the proposition contradicting the original proposition is false. Proof of many mathematical propositions, when using the direct card method is more troublesome or even impossible, if the proper use of reverse card method, can often have better results. Proof of proof of the general steps are: ① anti-set. Suppose the conclusion of the original proposition does not hold, that is contradictory to it