Let
be a convex hexagon all of whose sides are tangent to a circle
with centre
. Suppose that the circumcircle of triangle
is concentric with
. Let
be the foot of the perpendicular from
to
. Suppose that the perpendicular from
to
intersects the line
at a point
. Let
be the foot of the perpendicular from
to
. Prove that
.
Proposed by Japan
%V0
Let $ABCDEF$ be a convex hexagon all of whose sides are tangent to a circle $\omega$ with centre $O$. Suppose that the circumcircle of triangle $ACE$ is concentric with $\omega$. Let $J$ be the foot of the perpendicular from $B$ to $CD$. Suppose that the perpendicular from $B$ to $DF$ intersects the line $EO$ at a point $K$. Let $L$ be the foot of the perpendicular from $K$ to $DE$. Prove that $DJ=DL$.
Proposed by Japan