1995. Circumcenter at Midpoint of BC

1991. Circumcenter On Euler Line

1988. Circumcenters On Euler Line

 Let ABC be a triangle with P, Q are two points on Euler line of ABC.

A',B',C' are inverse images of A,B,C through circle diameter PQ.

* Circumcenter of  A'B'C' lies on Euler line of ABC.

1987. Circumcenter On Euler Line

 Let H=X(4)-Orthocenter of ABC. A1B1C1 cevian triangle of H. B1A, C1A are reflections of B1, C1 on A.

LA, line through B1A, C1A. define LB, LC cyclically.

A2B2C2 triangle bounded by lines LA, LB, LC.

* Circumcenter of  A2B2C2 lies on Euler line of ABC.

1986. Circumcenters On Euler Line

1983. A Circumcircle Through Circumcenter of ABC

1977. Triangles With Same Centroid

1973. A Construction For X(10020) = 22nd HATZIPOLAKIS-MONTESDEOCA POINT

1968. Concyclic Points

1967. Concyclic Points

1964. A Construction For X(18569)

 Let A1B1C1 reflection triangle of X(3)-circumcenter on the side lines of ABC.

Tangents to circumcircle of A1B1C1 at A1, B1, C1 form a triangle A2B2C2.*

*Circumcenter of A2B2C2 lies on Euler line of ABC. It's X(18569).

1963. A Triangle Inscribed In Nine-Point Circle

 Let A1B1C1 median triangle of ABC.

A2: Inverse of X(3)-Circumcenter of ABC in the circle with diameter B1C1. 
Define B2, C2 cyclically.

*A2B2C2 is inscribed in the Nine-Point Circle of ABC.

1958. A Circumcenter On Euler Line of ABC

1947. A Conic Problem

1943. Four Congruent Circles

1942. Right Triangles Inscribed In Feuerbach Hyperbola

1938. Collinear Points

1931. A Circumcenter On Euler Line

1928. A Conic Centered At X(1147) Dedicated To Sir Francisco Javier García Capitán on his birthday!

1920. A Line Perpendicular To Euler Line