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判定直线平行的方法很多,在“平行线”这一节教材中介绍了如下的五种方法: 1.二直线平行于同一直线,则此二直线平行. 2.在同一平面内,二直线垂直于同一直线,则此二直线平行.3.二直线被第三条直线所截,同位角相等,则此二直线平行, 4.二直线被第三条直线所截,内错角相等,则此二直线平行。 5.二直线被第三条直线所截,同旁内角互补,则此二直线平行. 最常用的是最后面的三个方法.这里举几个简单的例子说明.
There are many ways to determine the parallelism of a line. The following five methods are described in the textbook “Parallel Lines”: 1. Two lines are parallel to the same line, and the two lines are parallel. 2. In the same plane, the two lines are vertical. In the same straight line, the two straight lines are parallel. 3. The two straight lines are cut by the third straight line. If the isotropic angle is equal, the two straight lines are parallel. 4. The second straight line is cut by the third straight line, and the internal angle is equal. These two lines are parallel. 5. The two straight lines are truncated by the third straight line and are complementary to the side internal angles. The two straight lines are parallel. The most commonly used are the last three methods. Here are a few simple examples.