{A A' B B' : Type} (h : A + B <~> A' + B') (Ha : forall a:A, is_inl (h (inl a))) (Hb : forall b:B, is_inr (h (inr b))) : B <~> B' := Build_Equiv _ _ (unfunctor_sum_r h Hb) (isequiv_unfunctor_sum_r h Ha Hb).
Require Import HoTT.Basics. Require Import Types.Empty Types.Unit Types.Prod Types.Sigma. Require Import Types.Bool.