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设直线l与x轴的夹角为α,A,B是l上的任意两点.(1)若A、B两点在x轴上的射影的横坐标分别为x1、x2,则
Let the angle between the line l and the x axis be α, and A and B be any two points on l. (1) If the abscissas of the two points A and B on the x axis are x1 and x2 respectively, then