在立体几何题中,某些特殊图形中的二面角有时只给出一个公共点,因而二面角的棱是哪条直线或线段不明确.此类问题俗称“无棱”二面角问题.由于新教材引入了向量知识,所以立体几何中的二面角的大小求解方法在以往传 In the three-dimensional geometry problem, the dihedral angle in some special graphs sometimes only gives a common point, so the dihedral angle of the edge is which line or line is not clear. Such issues are commonly known as Angle problem.As a result of the introduction of the new textbook vector knowledge, so the geometry of the dihedral angle of the solution method in the past