求一个二面角的平面角的大小是高中立体几何的一个重要内容 ,也是一个难点 .学生往往不是不会计算 ,而是找不到二面角的平面角 .二面角的平面角定义告诉我们 :以二面角棱上任意一点为端点 ,在两个面内分别作垂直于棱的两条射线 ,这两条射线所成的角叫做二面角的平面角 .我们可? Finding the size of a plane angle with a dihedral angle is an important content of the high school stereo geometry, and it is also a difficult point. Students often do not calculate, but can not find the planar angle of the dihedral angle. The definition of the planar angle of the dihedral angle tells We use two points on each side of the two-sided corner to make two rays perpendicular to the edge. The angle formed by these two rays is called the plane angle of the dihedral angle. Can we?