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Make a straight line through a vertex of a polygon. After cutting off two corners of the polygon, the sum of its internal angles is 1260 degrees. What is the number of original sides of the polygon?
The sum of inner angles of the original polygon is 1260 + 180 * 2 = 1620
1620/180=9
9-1 = 8, so it turns out to be octagonal
As shown in the figure, the lengths of AB, BC and Ca on the three sides of △ ABC are 20, 30 and 40 respectively. The three bisectors divide △ ABC into three triangles, so s △ ABO: s △ BCO: s △ Cao equals ()
A. 1：1：1B. 1：2：3C. 2：3：4D. 3：4：5
The ratio of the area of triangles with the same height and different bottom is the ratio of the bottom
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