鸽巢：“证明策略”和“数学定理” In its popular form,the principle says that if there are more pigeons than holes,then at least one hole is the home of more than one pigeon. Theorem 21.2 (Pigeonhole principle). Let m andn be positive integers with m n,andletf be a map satisfying f:{1,.,ml→{1，.，nl.Then f is not one-to-one. The proof of the pigeonhole principle summarizes much of what you learned:mathematical induction,proof in cases,and one-to-one functions. 问题9： 你能简述一下这个证明的基本思路吗？鸽巢： “证明策略”和“数学定理