## Σάββατο, 14 Σεπτεμβρίου 2013

### PRIZE (Re: ORTHOCENTER - REFLECTIONS - CONCURRENT CIRCLES)

[APH]: In fact we can take any point P (instead of H) and any points O1,O2,O3 on the circumcircles of PBC,PCA,PAB, resp.

Then the circumcircles of the triangles

AO2O3, BO3O1, CO1O2

are concurrent.

Anopolis #850

For a proof I offer the book:

R. G. SANGER: SYNTHETIC PROJECTIVE GEOMETRY (1939)

APH

## Πέμπτη, 12 Σεπτεμβρίου 2013

### CONCYCLIC

RE: [EGML] CONIC - LOCUS

Posted By: cesar_e_lozada

Fri Sep 6, 2013 10:28 pm

Dear Antreas:

They are concyclic for all points P.

The center of their circle is the complement of the isotomic of P.

Regards

Cιsar Lozada

De: Anopolis@yahoogroups.com [mailto:Anopolis@yahoogroups.com] En nombre de Antreas Hatzipolakis

Enviado el: Jueves, 05 de Septiembre de 2013 06:28 p.m.

Para: anopolis@yahoogroups.com

Asunto: [EGML] CONIC - LOCUS

Let ABC be a triangle and A'B'C' the cevian triangle of P.

Denote:

Ab, Ac = the intersections of the circles with diameters BC, AA'

(near to B,C, resp.)

Bc, Ba = the intersections of the circles with diameters CA, BB'

Ca, Cb = the intersections of the circles with diameters AB, CC'

For P = H, the six points are concyclic.

For which P's are the six points lying on a conic?

APH

Anopolis #956

## Πέμπτη, 5 Σεπτεμβρίου 2013

### INTEGER SEQUENCES

In the book:

Marc Barbut, Bernard Monjardet: Ordre et Classification: Algebre et Combinatoire. Tome II. Hachette Universite, Paris, 1970.

are listed some integer sequences.

In pp. 44-46 the following:

1,3,19,219,4231,130023,6129859,.... It is A001035 in OEIS (The On-Line Encyclopedia of Integer Sequences)

1,4,29,355,6942,209527,9535241..... It is A000798 in OEIS

1,2,5,16,63,316,..... NOT FOUND IN OEIS

1,3,9,33,139,.... It is A001930 in OEIS 1,3,13,75,541,4683,47293,... It is A000670 in OEIS

In p. 101 the following:

1,2,5,,15,52,203,876,... It is A056273 in OEIS

0,1,3,7,15,31,63,.... It is A000225 in OEIS

0,0,1,6,25,90,301,... It is A000392 in OEIS

0,0,0,1,20,65,350,... NOT FOUND IN OEIS

0,0,0,0,1,15,140,... NOT FOUND IN OEIS

In pp. 165-166 the following:

1,4,18,166,7579,7828352,2414682040996,... It is A007153 in OEIS

1,3,8,28,208,.... NOT FOUND IN OEIS

1,2,4,12,81,... It is A001206 in OEIS

1,1,2,3,7,30,703,... NOT FOUND IN OEIS

BIBLIOGRAPHY:

For pages 1-78:

For pages 83-166:

## Τετάρτη, 4 Σεπτεμβρίου 2013

### PRIZE FOR CONCURRENT CIRCLES CONJECTURE

This "theorem" (conjecture) is still unproved (quoetd below).

Seiichi Kirikami has computed the coordinates for (P, P*) = (G, K)

Available here: Hyacinthos #21992

I offer the following books for proofs:

1. For an analytic proof by computing the homogeneous coordinates of the concurrence points:

RICHARD HEGER: ELEMENTE DER ANALYTISCHEN GEOMETRIE IN HOMOGENEN COORDINATEN (1872)

2. For a synthetic proof:

FRANK MORLEY & F. V. MORLEY: INVERSIVE GEOMETRY

3. For any other proof (by complex numbers, etc):

C. ZWIKKER: THE ADVANCED GEOMETRY OF PLANE CURVES AND THEIR APPLICATIONS.

Antreas

--- In Anopolis@yahoogroups.com, "Antreas" wrote:

>

> Let ABC be a triangle and P,P* two isogonal conjugate points.

> Denote: H1,H2,H3 = the orthocenters of PBC, PCA, PAB, resp. and

> Ha,Hb,Hc = the orthocenters of P*BC, P*CA, P*AB, resp.

>

> The circumcircles of:

> (1) H1HbHc, H2HcHa, H3HaHb

> (2) HaH2H3, HbH3H1, HcH1H2

>

> are concurrent.

>

> Figure: Here

>

> If P = (x:y:z), which are the points of concurrences?

>

> APH

>