proposition: Corollary join_join_power A n m : Join (join_power A n) (join_power A m) <~> join_power A (n + m)%nat.
proof: Proof. induction n as [|n IHn]. 1: exact (equiv_join_empty_left _). simpl. refine (_ oE (join_assoc _ _ _)^-1%equiv). exact (equiv_functor_join equiv_idmap IHn). Defined.
imports: Basics Types WildCat Join.Core Join.TriJoin Spaces.Nat.Core