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Inner García Triangle


InnerGarciaTriangle

The inner García triangle of a reference triangle ABC is obtained by reflecting its incenter I in the perpendicular bisectors of the three sides. Equivalently, it is obtained by reflecting the vertices of the outer García triangle across the corresponding sidelines of ABC (García 2014, 2016).

Writing a=BC, b=CA, and c=AB, its A-vertex has homogeneous barycentric coordinates

 A_i=(a^2,ac-b^2+c^2,ab+b^2-c^2),

with the other two vertices obtained cyclically (Kimberling).

For a nonequilateral reference triangle, its circumcircle has the same circumcenter O as ABC and passes through I (García 2014). Its circumradius is therefore

 R_i=OI=sqrt(R(R-2r)),

where R and r are the circumradius and inradius of ABC, using the Euler triangle formula. In this case, the inner García triangle is inversely similar to ABC with scale factor OI/R. For an equilateral triangle, I=O and all three constructed vertices coincide.

The García reflection triangle instead uses point reflections of the excenters in the side midpoints.


See also

Circumcenter, García Reflection Triangle, Incenter, Outer García Triangle, Perpendicular Bisector, Reflection, Reflection Triangle

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References

García, E. A. J. "A Note on Reflections." Forum Geom. 14, 155-161, 2014. https://drive.google.com/file/d/1HgLcT5S9immBULeiMr1IqPHbSCY4OTdo/view.García, E. J. "The Outer/Inner Garcia Triangle." GeoDom. Aug. 24, 2016. https://geometriadominicana.blogspot.com/2016/08/the-outerinner-garcia-triangle.html.Kimberling, C. "Encyclopedia of Triangle Centers: X(5692)=Centroid of the Inner-Garcia Triangle." https://faculty.evansville.edu/ck6/encyclopedia/ETCPart4.html#X5692.

Cite this as:

Weisstein, Eric W. "Inner García Triangle." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/InnerGarciaTriangle.html

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