"May 24, 2021, 3:26 PMInversion about $(O)$ preserves $(BDA_1)$, hence $(O)$ is a $B$-appolonian circle of $BDA_1$ with isodynamic points on it. The same with other triangles.", zuss77.
Let H=X(4)-Orthocenter of ABC. A 1 B 1 C 1 cevian triangle of H. B1 A , C1 A are reflections of B1, C1 on A. L A , line through B1 A , C1...
"May 24, 2021, 3:26 PM
ReplyDeleteInversion about $(O)$ preserves $(BDA_1)$, hence $(O)$ is a $B$-appolonian circle of $BDA_1$ with isodynamic points on it. The same with other triangles.", zuss77.