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人教版《几何》第一册17页第6题是:在图1中的两条直线上,各有哪几条线段?像这样的计数题,如果先找出规律再数,就可避免重复和遗漏.这里以第二条直线为例来说明这个计数规律:以A为一个端点的线段
The sixth question of the 17th page of the first edition of the PEP “Geometry” is: In the two straight lines in Figure 1, there are several line segments? If you want to find the number of rules, you can avoid Repeat and omissions. Here is a second straight line to illustrate this counting rule: Line segment with A as an endpoint