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空间的角是最基本的几何量之一.二面角的平面角是其中很重要的一类角,空间图形中点、线、面的位置关系常用它进行定量分析.它的构造是解题的关键所在.只有找到题目中二面角的平面角的恰当位置,才能搭起已知与未知之间的桥梁.因此,熟悉和掌握基本图形结构中各种二面角的平面角的构造方法,是同学们求解与二面角相关问题的必经之路.下文从二面角结构的“棱”和“半平面的垂线”入手,例谈三种二面角的平面角的基本构造方法.二面角的平面角的构造要符合准确性、可求性、易求性三原则.
The angle of space is one of the most basic geometric quantities. The plane angle of the dihedral angle is one of the important angles. The positional relationship between points, lines, and surfaces in a spatial graph is commonly used for quantitative analysis. Its construction is a problem-solving problem. The key to this is to find bridges between known and unknown only by finding the proper position of the dihedral plane angles in the subject. Therefore, familiarize with and master the construction methods for the planar angles of various dihedral angles in the basic graphic structure. , is the only way for students to solve the problems related to the dihedral angle. In the following, starting from the “edges” of the dihedral structure and the “perpendicular line of the half plane”, consider the basic structure of the plane angles of the three dihedral angles. Methods. The construction of the planar angles of dihedral angles must conform to the three principles of accuracy, applicability, and easiness of seeking.