Let
be a triangle with circumcircle
and
a line without common points with
. Denote by
the foot of the perpendicular from the center of
to
. The side-lines
intersect
at the points
different from
. Prove that the circumcircles of the triangles
,
and
have a common point different from
or are mutually tangent at
.
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Let $ABC$ be a triangle with circumcircle $\omega$ and $l$ a line without common points with $\omega$. Denote by $P$ the foot of the perpendicular from the center of $\omega$ to $l$. The side-lines $BC,CA,AB$ intersect $l$ at the points $X,Y,Z$ different from $P$. Prove that the circumcircles of the triangles $AXP$, $BYP$ and $CZP$ have a common point different from $P$ or are mutually tangent at $P$.