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 $OP$.