Paper 1, Section I, F
Part IB, 2013
Let and be ultraparallel geodesics in the hyperbolic plane. Prove that the have a unique common perpendicular.
Suppose now are pairwise ultraparallel geodesics in the hyperbolic plane. Can the three common perpendiculars be pairwise disjoint? Must they be pairwise disjoint? Briefly justify your answers.