(f : P -> Q) (x : P) : O_rec f (to O P x) = f x := (fst (extendable_to_O O 1%nat) f).
Require Import HoTT.Basics HoTT.Types. Require Import Equiv.BiInv Extensions HProp HFiber NullHomotopy Limits.Pullback. Require Import Homotopy.IdentitySystems. Require Import Colimits.Pushout.