近日,笔者在高三教学调研中通过听课交流发现,部分教师在对立体几何一道经典试题讲解时,辅助平面的确定及其书写的规范性存在问题,因此撰此短文,供同行们教学参考.题:如图,已知平面α∩平面β=b,直线a//α,a//β,求证:a//b.我们知道,本题的解答是利用线面平行性质定理将已知的线面平行转化成线线平行,再逐步通过线面平行判定定理和性质定理以及平 Recently, the author in the senior high school teaching research found through the lectures, some teachers on the three-dimensional geometry of a classic test to explain, the auxiliary plane to determine and write the normative problems, so this essay for peer teaching reference. : As shown, the known plane α ∩ plane β = b, the line a // α, a // β, verify: a // b. We know that the answer to this question is to use the line parallel property theorem to know the line Parallel parallel conversion into parallel lines, and then gradually through the plane parallel to determine the theorem and the nature of theorem and peace