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Second Neuberg Triangle


NeubergTriangles

The triangle DeltaN_1N_2N_3 formed by joining a set of three Neuberg centers (i.e., centers of the Neuberg circles) obtained from the edges of a given triangle DeltaA_1A_2A_3 (left figure). Similarly, a second set of three Neuberg circles with centers N_1^', N_2^', and N_3^' can be obtained from the main circles by reflection in their respective sides of the triangle, producing the second Neuberg triangle DeltaN_1^'N_2^'N_3^' (right figure).

The second Neuberg triangle has trilinear vertex matrix

 [abc(a^2+b^2+c^2) c(c^4-a^2c^2-b^2c^2-2a^2b^2) b(b^4-a^2b^2-c^2b^2-2a^2c^2); c(c^4-a^2c^2-b^2c^2-2a^2b^2) abc(a^2+b^2+c^2) a(a^4-b^2a^2-c^2a^2-2b^2c^2); b(b^4-a^2b^2-c^2b^2-2a^2c^2) a(a^4-b^2a^2-c^2a^2-2b^2c^2) abc(a^2+b^2+c^2)].
(1)
NeubergTriangleCentroids

The triangle centroid G_N of DeltaN_1N_2N_3 is coincident with the triangle centroid G_A of DeltaA_1A_2A_3 (Gallatly 1913; Johnson 1929, p. 288; left figure). Similarly, the centroids of DeltaA_1A_2A_3 and DeltaN_1^'N_2^'N_3^' also coincide (right figure).

NeubergTriangleLines

The lines A_1N_1^', A_2N_2^', A_3N_3^' concur at a point having equivalent triangle center functions

alpha_(262)=sec(A-omega)
(2)
alpha_(262)=(bc)/(2b^2c^2-a^4+a^2(b^2+c^2)),
(3)

which is Kimberling center X_(262) (right figure; Grinberg 2003).


See also

First Neuberg Triangle

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References

Gallatly, W. The Modern Geometry of the Triangle, 2nd ed. London: Hodgson, 1913.Grinberg, D. "Neuberg triangles, X(262) - Two Tarry points? Two 3rd Brocard points? [typos corrected]." geometry-college@mathforum.org mailing list. 12 Jan 2003.Johnson, R. A. Modern Geometry: An Elementary Treatise on the Geometry of the Triangle and the Circle. Boston, MA: Houghton Mifflin, 1929.

Referenced on Wolfram|Alpha

Second Neuberg Triangle

Cite this as:

Weisstein, Eric W. "Second Neuberg Triangle." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/SecondNeubergTriangle.html

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