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先给出一个定义:经过同一点的若干条直线(至少3条)所组成的图形叫直线束.定理:两条平行直线被直线束所截,截得的对应线段成比例.如图1,已知直线l1、l2、l3…交于点O,直线a∥b,且直线a、b分别与直线
First, we give a definition: A straight line consists of a number of straight lines (at least 3 lines) passing through the same point. Theorem: Two parallel straight lines are cut by a straight line beam and the corresponding line segments are cut in proportion. It is known that the straight lines l1, l2, l3 ... intersect at the point O, the straight line a // b, and the straight lines a, b are respectively connected with straight lines