{A B} {f g : A -> B} {x1 x2 : A} (p : x1 = x2) (q : f x1 = g x1) r : ((ap f p)^ @ q) @ ap g p = r <~> DPath (fun x : A => f x = g x) p q r. Proof. apply equiv_concat_l, transport_paths_FlFr. Defined.
Require Import Basics. Require Import Types.Paths Types.Sigma Types.Forall.