∀ {α : Type u_1} {β : Type u_2} [inst : TopologicalSpace α] [inst_1 : AddCommGroup α] [inst_2 : LinearOrder α]
  [IsOrderedAddMonoid α] [OrderTopology α] {l : Filter β} {f g : β → α} {C : α},
  Filter.Tendsto f l Filter.atTop → Filter.Tendsto g l (nhds C) → Filter.Tendsto (fun x => f x + g x) l Filter.atTop