2018 USAMO Problems/Problem 5
Problem 5
In convex cyclic quadrilateral 
we know that lines 
and 
intersect at 
lines 
and 
intersect at 
and lines 
and 
intersect at 
Suppose that the circumcircle of 
intersects line 
at 
and 
, and the circumcircle of 
intersects line at 
and 
, where 
and 
are collinear in that order. Prove that if lines 
and 
intersect at 
, then 
