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Euclidean, hyperbolic, discrete, convex, coarse geometry, metric spaces, comparisons in Riemannian geometry, symmetric spaces.

1 vote
0 answers
158 views

A certain circle formed by perpendiculars

If six points are chosen, two points on each side of a triangle, such that they have the same ratio of distances to vertices, then the perpendicular lines through those points meet at six concyclic p …
Benjamin L. Warren's user avatar
5 votes
1 answer
526 views

Twin circles in a quadrilateral

The circumcenters of the four triangles of a complete quadrilateral along with the two points of completion form two congruent circles (in black). Surely this must've been done before - what's the fo …
Benjamin L. Warren's user avatar
0 votes
0 answers
77 views

Coordinates of the centers of the insphere and circumsphere

Suppose we are working in $\mathbb{R}^3$ space and we have four non-coplanar and non-collinear points, $(x_a, y_a, z_a)$, $(x_b, y_b, z_b)$, $(x_c,y_c, z_c)$, and $(x_d, y_d, z_d)$. How does one deter …
Benjamin L. Warren's user avatar
1 vote
0 answers
65 views

Name of the perspector of the orthic triangle and excentral triangle

The orthic triangle and tangential triangles of a given triangle are in perspective. What's the official kimberling center associated with this perspector?
Benjamin L. Warren's user avatar
3 votes
1 answer
278 views

Name this kimberling center

The lines which connect the vertices of a triangle with the tangent points between the Spieker circle and the medial triangle are concurrent. Which kimberling center does this point correspond to?
Benjamin L. Warren's user avatar
3 votes
1 answer
248 views

Nagel line of a tetrahedron?

It's well known that there is an analogy for the Euler line in a tetrahedron, but is there also an analogy for the nagel line of a tetrahedron? I can't seem to find any decent literature talking about …
Benjamin L. Warren's user avatar
0 votes
1 answer
131 views

Name this geometric point?

Is there a formal name for the point which is the reflection of the incenter about the circumcenter of a triangle?
Benjamin L. Warren's user avatar
2 votes
0 answers
137 views

Name of this geometric point? [closed]

Draw a triangle. At one of the vertices, draw a line through it that bisects the angle. At each of the other two vertices, draw a line through it which is perpendicular to the line that bisects its an …
Benjamin L. Warren's user avatar