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两条直线被第三条直线所截 ,得 8个角 ,常称为“三线八角” .所构成的同位角、内错角、同旁内角与今后识别平行线的关系密切 ,现将识别此 3类角的方法简述如下 :[预备知识 ]如图 1 ,对于直线l来说 ,∠1在直线l的上方 ,∠2在直线l的下方 .两条直线a、b(简称“两线”)将平面分成A
The two straight lines are truncated by the third straight line, resulting in eight corners, often referred to as “three-line octagonal.” The azimuth angle, the inner angle, the inner angle, and the adjacent side angle are closely related to the future recognition of parallel lines. The methods of the 3 types of angles are briefly described as follows: [Preliminary knowledge] As shown in Fig. 1, for a straight line l, ∠1 is above the line l, ∠2 is below the line l. Two lines a, b (referred to as “two lines”) ") Divide the plane into A