在学习相交线的内容时,我们曾经遇到过类似下面的问题:如图1,在8×8的方格纸中,试用直尺过点C画直线l的垂线.作图步骤为:(1)找出以直线l上的一部分为对角线的长方形,如图2中,竖直的1×3的长方形为所找长方形;(2)在方格纸中找出以点C为一个顶点的3×1的水平长方形,如图2;(3)过点C画该长方形的对角线所在的直线e,则直线e就是所求的直线. In studying the content of intersecting lines, we have encountered similar problems as follows: Figure 1, in the 8 × 8 cellophane paper, try the ruler over C straight line drawn l C drawing steps: (1) to find a part of the line l diagonal rectangle, as shown in Figure 2, the vertical rectangle of 1 × 3 for the rectangle to find; (2) in the grid paper to find the point C A 3 × 1 horizontal rectangle of a vertex, as shown in FIG. 2; (3) If a line c where the diagonal of the rectangle is found is located at point C, the straight line e is the desired straight line.