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| | ipedia.com: Circle Article (Site not responding. Last check: 2007-10-07) |
 | | If only (part of) a circle is known, then the circle's center can be constructed as follows: take two non-parallel chords, construct perpendicular lines on their midpoints, and find the intersection point of those lines. |
 | | A part of the circumference bound by two radii is called an arc, and the area (i.e., the slice of the disk) within the radii and the arc is a sector. |
 | | Every triangle gives rise to several circles: its circumcircle containing all three vertices, its incircle lying inside the triangle and touching all three sides, the three excircles lying outside the triangle and touching one side and the extensions of the other two, and its nine point circle which contains various important points of the triangle. |
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