{A B : Type} {f g : A -> B} (p : forall x, f x = g x) {x y : A} (q : x = y) {w : B} (r : w = f x) : (r @ ap f q) @ p y = (r @ p x) @ ap g q. Proof. destruct q; simpl. induction (p x). reflexivity. Defined.
Require Import Basics.Overture Basics.Tactics.