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在同一平面内,不相交也不重合的两条直线叫作平行线。平行线在生产生活中具有十分广泛的应用,如下面各图所示,体育锻炼用的双杠、晾毛巾的架子、火车行驶的铁轨等都是平行线。画已知直线的平行线时,要用三角板、直尺等工具,还要边画边看边想,不少同学感到困难重重。怎么办?大家不妨按如下五步试一试:一放。就是把直尺放在直线上,与已知直线相交,如图1。
In the same plane, the two straight lines that do not intersect or coincide are called parallel lines. Parallel lines in the production of life has a very wide range of applications, as shown in the following figures, sports parallel bars, hanging towel rack, the train driving the rails are parallel lines. Drawing parallel lines known straight line, the use of board, ruler and other tools, but also while drawing and watching, many students feel difficult. How to do? You may wish to try the following five steps: a release. Is the ruler on a straight line, intersecting the known straight line, shown in Figure 1.