在各类试题中，曾发现有这样一道立体几何题：（如图1）在正三棱柱ABC—A_1B_1C_1年它又换上新装出现在普通高等学校招生全国统一考试的“三南”试题中，可见它是一道好题，引起笔者的兴趣．将探索所得到的结果公布于后，供同行们参考．［思路1］；本题的意图要证A_1B⊥A_1C， In various questions, it has been found that there is such a three-dimensional geometric problem: (Figure 1) in the positive triangular prism ABC-A_1B_1C_1 years it is replaced with a new installation appears in the “three South” test of the National Higher Education Admissions Unified Examination, can be seen It is a good question that aroused the author’s interest. The results of the exploration are published for reference by their peers. [Thought 1]; The intention of this question is to prove A_1B⊥A_1C,