| | Math Forum - Geometry Problem of the Week |
 | | Since the perpendicular bisector of any chord goes through the center of the circle, a polygon can be circumscribed by a circle only if the perpendicular bisectors of each side of the polygon converge at a single point, or the midpoint of the circle (see figure X). |
 | | I tried drawing perpendicular bisectors to each side of a polygon and found that if they all meet at one point, then a single circle can be drawn with its centre at that point, which will circumscribe the whole polygon, i.e. |
 | | Hence, using the previous part of the problem, the perpendicular bisectors of the sides of the polygon would all pass through the point O. So, one way to test would be to construct all the perpendicular bisectors of the sides and see if they all meet at one point. |
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