Let
,
,
,
,
be points such that
is a cyclic quadrilateral and
is a parallelogram. The diagonals
and
intersect at
and the rays
and
intersect at
. Prove that
.
%V0
Let $A$, $B$, $C$, $D$, $E$ be points such that $ABCD$ is a cyclic quadrilateral and $ABDE$ is a parallelogram. The diagonals $AC$ and $BD$ intersect at $S$ and the rays $AB$ and $DC$ intersect at $F$. Prove that $\sphericalangle{AFS}=\sphericalangle{ECD}$.
Školjka