Dao's blog: 12-Viet Nam Hexagon

Let $ABC$ be a triangle, $D$ be a in triangle. $AD,BD,CD$ meet $(ABC)$ again at $A_1,B_1,C_1$ . $H$ is on $BD$ such that $HA$ perpendicular with $AB$ . $A_b$ is circumcenter of circle $(AB_1H)$ . Define $A_b,A_c,B_a,B_c,C_a,C_b$ cyclically. Then six points $A_bC_bC_aB_aB_cA_c$ are the hexagon circumscribed. I named the result is Viet Nam hexagon