| 词条 | Morley centers |
| 释义 |
In geometry the Morley centers are two special points associated with a plane triangle. Both of them are triangle centers. One of them called first Morley center[1] (or simply, the Morley center[2] ) is designated as X(356) in Clark Kimberling's Encyclopedia of Triangle Centers, while the other point called second Morley center[1] (or the 1st Morley–Taylor–Marr Center[2]) is designated as X(357). The two points are also related to Morley's trisector theorem which was discovered by Frank Morley in around 1899. DefinitionsLet DEF be the triangle formed by the intersections of the adjacent angle trisectors of triangle ABC. Triangle DEF is called the Morley triangle of triangle ABC. Morley's trisector theorem states that the Morley triangle of any triangle is always an equilateral triangle. First Morley centerLet DEF be the Morley triangle of triangle ABC. The centroid of triangle DEF is called the first Morley center of triangle ABC.[1][3] Second Morley centerLet DEF be the Morley triangle of triangle ABC. Then, the lines AD, BE and CF are concurrent. The point of concurrence is called the second Morley center of triangle ABC.[1][3] Trilinear coordinatesFirst Morley centerThe trilinear coordinates of the first Morley center of triangle ABC are [1] cos ( A/3 ) + 2 cos ( B/3 ) cos ( C/3 ) : cos ( B/3 ) + 2 cos ( C/3 ) cos ( A/3 ) : cos ( C/3 ) + 2 cos ( A/3 ) cos ( B/3 ). Second Morley centerThe trilinear coordinates of the second Morley center are sec ( A/3 ) : sec ( B/3 ) : sec ( C/3 ). References1. ^1 2 3 4 {{cite web|last=Kimberling|first=Clark|title=1st and 2nd Morley centers|url=http://faculty.evansville.edu/ck6/tcenters/recent/morley.html|accessdate=16 June 2012}} 2. ^1 {{cite web|last=Kimberling|first=Clark|title=X(356) = Morley center|url=http://faculty.evansville.edu/ck6/encyclopedia/ETC.html|work=Encyclopedia of Triangle Centers|accessdate=16 June 2012}} 3. ^1 {{cite web|last=Weisstein|first=Eric W|title=Morley Centers|url=http://mathworld.wolfram.com/MorleyCenters.html|work=Mathworld – A Wolfram Web Resource|accessdate=16 June 2012}} 1 : Triangle centers |
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