fact: Definition continuous2d_base_at {U V W : TopologicalSpace} (f : U → V → W) (x : U) (y : V) base_x base_y base_fxy := is_lim_base (λ z : U × V, f (pr1 z) (pr2 z)) (FilterDirprod (locally_base x base_x) (locally_base y base_y)) (f x y) base_fxy.
imports: UniMath.Foundations.All UniMath.MoreFoundations.All UniMath.Topology.Filters UniMath.Algebra.Groups UniMath.Algebra.DivisionRig UniMath.Algebra.ConstructiveStructures