求二面角的大小是历届高考的重点内容之一,其关键是要作出二面角的平面角,这恰好是不少同学感到头疼的问题.下面介绍几种作二面角的平面角的常用技巧.1抓住共底的等腰三角形作平面角如果2个共底边的等腰三角形ABC和DBC分别在二面角αlβ的2个半平面上,则可作出BC边的中点E,连结 The size of the dip angle is one of the key contents of the previous college entrance examination. The key is to make a dihedral plane angle. This happens to be a headache for many students. The following describes several plane angles for dihedral angles. Commonly used techniques. 1 Grasp the isosceles triangle of the common bottom as the plane angle If the two isosceles triangles ABC and DBC of the common bottom are respectively on the two half planes of the dihedral angle αlβ, the midpoint of the BC side can be made. ,link