利有法向量解决立体几何问题是近几年高考的一个新亮点.众所周知,二面角的大小与其两个面的法向量的夹角相等或互补,但“相等”还是“互补”这个问题始终困扰着大家,即使是高考试卷的解答也没能得到彻底的解决,总让人觉得美中不足.本文拟给出一个简单的判定方法.引理向量m是平 Lee has a normal vector to solve the problem of three-dimensional geometry is a new bright spot in college entrance examination in recent years.As we all know, the size of the dihedral and the angle between the two faces of the normal vector or complementary, but “equal” or “complementary” the problem has always been Disturbing everyone, even if the answers to the entrance examination papers have not been completely solved, people always think that the fly in the ointment.This paper is intended to give a simple decision method. Lemma m is flat