{A B C D} (f : A -> B) (g : C -> D) (h : A -> C) (k : B -> D) (p : k o f == g o h) `{IsEquiv _ _ f} `{IsEquiv _ _ h} `{IsEquiv _ _ k} : IsEquiv g. Proof. refine (@cancelR_isequiv _ _ _ h g _ _). refine (isequiv_homotopic _ p). Defined.
Require Import