释义 |
CircumradiusThe radius of a Triangle's Circumcircle or of a Polyhedron's Circumsphere, denoted . For a Triangle,
| (1) |
where the side lengths of the Triangle are , , and .
This equation can also be expressed in terms of the Radii of the three mutually tangentCircles centered at the Triangle's Vertices. Relabeling the diagram forthe Soddy Circles with Vertices , , and and the radii , , and, and using
then gives
| (5) |
If is the Circumcenter and is the triangle Centroid, then
| (6) |
| (7) |
| (8) |
| (9) |
| (10) |
(Johnson 1929, pp. 189-191). Let be the distance between Inradius and circumradius ,. Then
| (11) |
| (12) |
(Mackay 1886-87). These and many other identities are given in Johnson (1929, pp. 186-190).
For an Archimedean Solid, expressing the circumradius in terms of the Inradius and Midradius gives
for an Archimedean Solid.See also Carnot's Theorem, Circumcircle, Circumsphere References
Johnson, R. A. Modern Geometry: An Elementary Treatise on the Geometry of the Triangle and the Circle. Boston, MA: Houghton Mifflin, 1929.Mackay, J. S. ``Historical Notes on a Geometrical Theorem and its Developments [18th Century].'' Proc. Edinburgh Math. Soc. 5, 62-78, 1886-1887.
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