proposition: Proposition h_sq_isotoid_idtoiso_2_1 {B : verity_double_bicat} (H : horizontally_saturated B) (HB_2_1 : hor_locally_univalent B) {x y : B} {h₁ h₂ : x --> y} (p : h₁ = h₂) : h_sq_isotoid_2_1 H HB_2_1 (h_sq_idtoiso_2_1 p) = p.
proof: Proof. unfold h_sq_idtoiso_2_1, h_sq_isotoid_2_1. etrans. { apply maponpaths. exact (homotweqinvweq (horizontal_square_weq_invertible_2cell H h₁ h₂) (idtoiso_2_1 h₁ h₂ p)). } apply isotoid_2_1_idtoiso_2_1. Qed.
imports: UniMath.MoreFoundations.All UniMath.CategoryTheory.Core.Prelude UniMath.CategoryTheory.TwoSidedDisplayedCats.TwoSidedDispCat UniMath.CategoryTheory.TwoSidedDisplayedCats.Isos UniMath.CategoryTheory.TwoSidedDisplayedCats.Univalence UniMath.CategoryTheory.TwoSidedDisplayedCats.Discrete UniMath.Bicategories.Core.Bicat UniMath.Bicategories.Core.Univalence UniMath.Bicategories.DoubleCategories.DoubleBicat.VerityDoubleBicat UniMath.Bicategories.DoubleCategories.DoubleBicat.DerivedLaws UniMath.Bicategories.DoubleCategories.DoubleBicat.UnderlyingCats UniMath.Bicategories.DoubleCategories.DoubleBicat.CellsAndSquares