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Mittenpunkt


Mittenpunkt

The mittenpunkt (also called the middlespoint) of a triangle DeltaABC is the symmedian point of the excentral triangle, i.e., the point of concurrence M of the lines from the excenters J_i through the corresponding triangle side midpoints M_i. It is commonly denoted D or M, has equivalent triangle center functions

alpha=b+c-a
(1)
alpha=cot(1/2A),
(2)

and is Kimberling center X_9 (Kimberling 1998, p. 66).

MittenpunktCollinear1
MittenpunktCollinear2
MittenpunktCollinear3

The mittenpunkt is collinear with the Gergonne point Ge and triangle centroid G, with GeG:GM=2:1. The mittenpunkt is also collinear with the Spieker center Sp and the orthocenter (Eddy 1990). Further, the mittenpunkt is collinear with the incenter I and symmedian point K of DeltaABC, with distance ratio

 (IM)/(MK)=-(2(a^2+b^2+c^2))/((a+b+c)^2).
(3)

Distances from the mittenpunkt to several other named triangle centers include

MCl=-(8abc(a+b+c)^2ILr^2)/((a^2-2ba-2ca+b^2+c^2-2bc)(a^5-ba^4-ca^4+2bc^2a^2+2b^2ca^2-b^4a-c^4a+2b^2c^2a+b^5+c^5-bc^4-b^4c))
(4)
MH=((a^3-ba^2-ca^2-b^2a-c^2a-2bca+b^3+c^3-bc^2-b^2c)IL)/((a+b+c)(a^2-2ba-2ca+b^2+c^2-2bc))
(5)
MI=(2(a^2+b^2+c^2)IK)/((a^2-2ab+b^2-2ac-2bc+c^2))
(6)
MK=((a+b+c)^2IK)/(a^2-2ab+b^2-2ac-2bc+c^2)
(7)
MSp=(2ILr^2)/(a^2-2ab+b^2-2ac-2bc+c^2),
(8)

where Cl is the Clawson point, H is the orthocenter, I is the incenter, K is the symmedian point, and Sp is the Spieker center.

The mittenpunkt is the center of the Mandart inellipse.


See also

Excenter, Excentral Triangle, Isogonal Mittenpunkt, Mandart Inellipse, Nagel Point

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References

Baptist, P. Die Entwicklung der Neueren Dreiecksgeometrie. Mannheim: Wissenschaftsverlag, p. 72, 1992.Eddy, R. H. "A Generalization of Nagel's Middlespoint." Elem. Math. 45, 14-18, 1990.Kimberling, C. "Central Points and Central Lines in the Plane of a Triangle." Math. Mag. 67, 163-187, 1994.Kimberling, C. "Triangle Centers and Central Triangles." Congr. Numer. 129, 1-295, 1998.Kimberling, C. "Mittenpunkt." http://faculty.evansville.edu/ck6/tcenters/class/mitten.html.Kimberling, C. "Encyclopedia of Triangle Centers: X(9)=Mittenpunkt." http://faculty.evansville.edu/ck6/encyclopedia/ETC.html#X9.

Referenced on Wolfram|Alpha

Mittenpunkt

Cite this as:

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

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