MEMO 2011 pojedinačno problem 3
Kvaliteta:
Avg: 3,5Težina:
Avg: 6,6 In a plane the circles
and
with centers
and
, respectively, intersect in two points
and
. Assume that
is obtuse. The tangent to
in
intersects
again in
and the tangent to
in
intersects
again in
. Let
be the circumcircle of the triangle
. Let
be the midpoint of that arc
of
that contains
. The lines
and
intersect
again in
and
, respectively. Prove that the line
is perpendicular to
.




























Izvor: Srednjoeuropska matematička olimpijada 2011, pojedinačno natjecanje, problem 3