fact: Definition circle_cover (t : RTop) : ProductTopology2 RTop RTop := (cos (2*PI*t), sin (2*PI*t)).
imports: Coq(Reals.Ratan Lia Lra Logic.IndefiniteDescription Program.Subset) ZornsLemma(Quotients) Topology(ProductTopology AdjunctionSpace SubspaceTopology RTopology RFuncContinuity Homeomorphisms)