2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/129391We prove that every compact plane billiard, bounded by a smooth curve, is insecure: there exist pairs of points $A,B$ such that no finite set of points can block all billiard trajectories from $A$ to $B$.Differential GeometryDynamical Systemstext