在立体几何中,用二面角的两个面的法向量的夹角求二面角的大小,是高考常考内容之一.而法向量的夹角与二面角的大小是相等或互补关系,因此,在各种情况下,能准确辨别法向量的夹角与二面角的大小是相等还是互补,是解决此类问题的关键. In solid geometry, using the angle between the two normals of the dihedrals to determine the dihedral angle is one of the most commonly used tests in the college entrance examination, while the angle between the normals and dihedrals is equal or complementary Therefore, under various circumstances, the key to solve these problems is to be able to accurately identify whether the angle between the normal vector and the dihedral angle is the same or not.