相交和平行是同一平面内两条直线的两种位置关系.在相交线的学习中,离不开邻补角和对顶角;在平行线的学习中,离不开同位角、内错角和同旁内角.因此,与相交线或平行线有关的问题常常以求角度和探索角为主.解答时,要注意灵活运用各种相关角的关系. Intersection and parallelism are two kinds of positional relationship of two straight lines in the same plane. In the study of the intersection line, it is inseparable from the adjacent complementary angle and the right angle; in parallel line learning, can not do without the same angle, Therefore, the problems associated with intersecting lines or parallel lines are often dominated by angles of view and exploratory angles. When answering, pay attention to the flexible use of the relationship between the various angles.