求二面角的大小是立体几何的一个重点,而求无棱二面角是该重点的难点.以下通过一道高考题介绍几种求无棱二面角的常用方法.1.找另一个公共点作棱根据公理2“如果两个平面有一个公共点,那么它们还有其它公共点,这些公共点的集合是一条直线”可知,若两个平面有两个公共点,则它们交于过这两点的直线.在二面角的两个半平面有一个公共 Seeking the size of the dihedral angle is a focus of the three-dimensional geometry, and find the non-edge dihedral angle is the focus of the difficulty. The following passage through a college entrance examination introduced several commonly used method of non-edge dihedral angle .1 find another public If the two planes have a common point, then they have other common points, and the set of common points is a straight line. "Knowing that two planes have two common points, they intersect At the straight line between these two points there is a public in the two half-planes of the dihedral