fact: Definition weqfromcoprodofstn_map (n m : nat) : (⟦n⟧ ⨿ ⟦m⟧) -> ⟦n+m⟧.
imports: UniMath.Foundations.NaturalNumbers UniMath.MoreFoundations.Tactics UniMath.MoreFoundations.DecidablePropositions UniMath.MoreFoundations.NegativePropositions