English
A version of the left inverse holds for general targets B1, using flip symmetry.
Русский
Версия левого обратного сохраняется для общего целевого пространства B1, с использованием симметрии flip.
LaTeX
$$$ associated_left_inverse' \{B_1 : BilinMap R M N\} (hB_1 : B_1.flip = B_1) : associatedHom S B_1.toQuadraticMap = B_1 $$$
Lean4
theorem associated_left_inverse {B₁ : BilinMap R M N} (h : ∀ x y, B₁ x y = B₁ y x) :
associatedHom S B₁.toQuadraticMap = B₁ :=
LinearMap.ext₂ fun x y ↦ by
rw [associated_toQuadraticMap, ← h x y, ← two_smul R, invOf_smul_eq_iff, two_smul, two_smul]