Let be the circumcentre, and be the circumcircle of an acute-angled triangle . Let be an arbitrary point on , distinct from , , , and their antipodes in . Denote the circumcentres of the triangles , , and by , , and , respectively. The lines , , perpendicular to , , and pass through , , and , respectively. Prove that the circumcircle of triangle formed by , , and is tangent to the line .
Let $O$ be the circumcentre, and $\Omega$ be the circumcircle of an acute-angled triangle $ABC$. Let $P$ be an arbitrary point on $\Omega$, distinct from $A$, $B$, $C$, and their antipodes in $\Omega$.
Denote the circumcentres of the triangles $AOP$, $BOP$, and $COP$ by $O_A$, $O_B$, and $O_C$, respectively.
The lines $\ell_A$, $\ell_B$, $\ell_C$ perpendicular to $BC$, $CA$, and $AB$ pass through $O_A$, $O_B$, and $O_C$, respectively.
Prove that the circumcircle of triangle formed by $\ell_A$, $\ell_B$, and $\ell_C$ is tangent to the line $OP$.