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上篇谈了一些常见的平面图形。本文将在介绍直线、平面间的位置关系的基础上谈淡长方体、正方体、圆柱体和圆锥体的概念及其直观图的画法。 一、空间两条直线间的位置关系 平面内的两条直线只有相交和平行两种位置关系。但在空间,两条直线还存在第三种位置关系——既不平行也不相交。这样两条直线称为异面直线。如图1中的a、b即为异面直线。如果把立交桥与桥下的公路都看成直线,那它们就是异面直线。
The first part of the talk about some common plane graphics. This article will introduce the straight line, the relationship between the basis of the plane on the basis of talk about pale cubes, cubes, cylinders and cones concept and its intuitive drawing method. First, the space between the two straight lines The relationship between the two planes in the plane only intersect and parallel two kinds of positional relationship. But in space, there is a third positional relationship between the two lines - neither parallel nor intersect. These two lines are called straight lines. As shown in Figure 1 a, b is a straight line of the opposite. If the overpass and the bridge under the road as a straight line, then they are straight lines.