HYACINTHOS 21468

Let La, Lb, Lc be the reflections of L in BC,CA,AB, resp. (concurrent
on the circumcircle).

Let Ab, Ac be the orth. projections of A' on Lb,Lc, resp. Similarly
Bc,Ba and Ca,Cb.

The circumcircles of A'AbAc, B'BcBa, C'CaCb are coaxial and their NPC
centers are
collinear. Which is this line ? Special case: L = Euler line.