{A B : Type} {f g : A -> B} {x1 x2 : A} (p : x1 = x2) (q : f x1 = g x1) : transport (fun x => f x = g x) p q = (ap f p)^ @ q @ (ap g p). Proof. destruct p; simpl. exact ((concat_1p q)^ @ (concat_p1 (1 @ q))^). Defined.
Require Import Basics.Overture Basics.Equivalences Basics.PathGroupoids Basics.Tactics.