Let k1,…,k5 be five circles in the plane such that k1 and k2 are externally tangent to each other at point T, k3 and k4 are externally tangent to both k1 and k2, k5 is externally tangent to k3 and k4 at points U and V, respectively, moreover k5 intersects k1 at P and Q, like shown in the figure.
Want a route through all this instead of an archive? The track
puts 2,604 problems in a working order, from Junior Challenge level to the IMO shortlist.