《几何》第一册(人教版试用修订本)第46页习题1.5的第4题中,借助东、南、西、北的方位,用射线来表示方向,我们常称这种角叫做方向角. 这种方向角表示有一定的要求.第一个字要先写南或北(即以南、北为基准),然后再写偏东或偏西多少度.如图1,射线OA表示的方向是北偏东30°(注意:不能写成东偏北60°),射线OB表示的方向是南偏西60°(注 In the fourth issue of Problem Set 1.5 (Question and Revision of the PEP Trial) on page 46, with the orientations of the east, south, west, and north, the directions are represented by rays. We often call this angle the direction. Angular. This direction angle indicates that there is a certain requirement. The first character must first be written south or north (ie, based on south and north), and then written to the east or west how many degrees. Figure 1, the ray OA said The direction is 30°east to the east (note: it cannot be written 60° east to north), and the direction represented by the ray OB is 60° south west (note