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### I, Concurrent Euler lines

(8)

[Le Viet An]: Let ABC be a triangle and IaIbIc the antipedal triangle of I. Let L be a line passing through I. Denote: A', B', C' = the orthogonal projections
Antreas Hatzipolakis

Jul 24

### H, perspective

(6)

[APH]: Let ABC be a triangle and A'B'C', A"B"C" the cevian, circumcevian triangles of H, resp. Let A* be the second intersection (other than A") of the
Antreas Hatzipolakis

Jul 23

### O, H, Reflections

(4)

[APH]: Let ABC be a triangle. The reflections of HA in OA, OB, OC bound a triangle Ta The reflections of HB in OA, OB, OC bound a triangle Tb The reflections
Antreas Hatzipolakis

Jul 20

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### Na, Concurrent Euler lines

(3)

[Tran Quang Hung] = buratinogigle (*) Let ABC be a triangle, A'B'C' the pedal triangle of I and A"B"C" the cevian triangle of the Nagel point Na. The Euler
Antreas Hatzipolakis

Jul 19

### A circle touching the incircle.

(3)

[Le Viet An]: Let ABC be a triangle, MaMbMc the cevian triangle of G and Fe the Feuerbach point. The line IG intersects MbMc, McMa, MaMb at Ka, Kb, Kc, resp.
Antreas Hatzipolakis

Jul 18

### Concurrent Euler lines

(13)

[APH]: Let ABC be a triangle. Denote: Ab,Ac = the orthogonal projections of A on IB, IC, resp. La = the Euler line of AAbAc Laa, Lab, Lac = the reflections of
Antreas Hatzipolakis

Jul 15

### A NPC touches the circumcircle

(4)

[Le Viet An] (*): Let ABC be a triangle and L a line passing through O. Denote: A',B',C' = the orthogonal projections of A,B,C on L, resp. La, Lb, Lc = the
Antreas Hatzipolakis

Jul 15

### Points on the circumcircle

(4)

[Le Viet An]: Let ABC be a triangle, L a line through O and P a point on the circumcircle (O) of ABC Denote: A1, B1, C1 = the intersections of the lines PA,
Antreas Hatzipolakis

Jul 13

### Point on the NPC

(5)

[APH]: Let ABC be a triangle and P a point. Denote: Ab, Ac = the orthogonal projections of A on PB, PC, resp. Similarly Bc, Ba and Ca, Cb. La, Lb, Lc = the
Antreas Hatzipolakis

Jul 13

### Feuerbach points, a NPC

(3)

[Le Viet An]: Let ABC be a triangle and Fe, Fa, Fb, Fc the Feuerbach points. Denote: PaPbPc = the pedal triangle of I. Qa, Qb, Qc = the orthogonal projections
Antreas Hatzipolakis

Jul 13

### X110, locus

(6)

[APH]: Let ABC be a triangle, P a point and A'B'C' the pedal triangle of P. Denote: Ea = the X110 of AB'C' (ie the point the reflections of the Euler line of
Antreas Hatzipolakis

Jul 4

### Concurrent Euler Lines

(19)

[APH]: Dear Mr rodinos (*), I have two new problems (and synthetic proofs): *Probelm 1*. Let Ia, Ib, Ic be A, B, C-excenters of a triangle ABC, resp. Let Ka,
Antreas Hatzipolakis

Jul 4

### Simson lines, locus

(5)

Let ABCD be a quadrangle. Denote: S = the Poncelet point of (ABCD) (ie the point the NPCs of BCD, CDA, DAB, ABC concur at) Ma, Mb, Mc, Md = the medial
Antreas Hatzipolakis

Jul 1

### Isogonal conjugate of Perspector lies on Euler line

(4)

[APH]: 1. Let ABC be a triangle and P a point. Denote: Pa, Pb, Pc = the reflections of P in BC, CA, AB, resp. D = AO /\ PbPc E = BO /\ PcPa F = CO /\ PaPb
Antreas Hatzipolakis

Jul 1

### O, Homothetic

(4)

[APH]: Let ABC be a triangle and A'B'C' the pedal triangle of a point P. Denote: Bc, Cb = the orthogonal projections of B', C' on AB, AC, resp. B3, C2 = the
Antreas Hatzipolakis

Jun 29

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## Trending Topics

See All- I, Concurrent Euler lines 8 Posts
- H, perspective 6 Posts
- O, H, Reflections 4 Posts
- Na, Concurrent Euler lines 3 Posts
- A circle touching the incircle. 3 Posts

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