English
There is an instance IsScalarTower for R, R and the PiTensorProduct: R R ⟨PiTensorProduct⟩ forms a scalar tower.
Русский
Существует экземпляр IsScalarTower для R, R и PiTensorProduct, образующий башню скаляров.
LaTeX
$$$ \text{instance } IsScalarTower R R (\PiTensorProduct(R, s)) $$$
Lean4
theorem range_inl : range (inl R M M₂) = ker (snd R M M₂) :=
by
ext x
simp only [mem_ker, mem_range]
constructor
· rintro ⟨y, rfl⟩
rfl
· intro h
exact ⟨x.fst, Prod.ext rfl h.symm⟩