English
In a tower F ⊆ K ⊆ A, if A is finite over F, then A is finite over K.
Русский
В башне F ⊆ K ⊆ A, если A конечно над F, то A конечно над K.
LaTeX
$$$\\text{Module.Finite } F A \\Rightarrow \\text{Module.Finite } K A$$$
Lean4
@[stacks 09G5]
theorem right [hf : Module.Finite F A] : Module.Finite K A :=
let ⟨⟨b, hb⟩⟩ := hf
⟨⟨b,
Submodule.restrictScalars_injective F _ _ <|
by
rw [Submodule.restrictScalars_top, eq_top_iff, ← hb, Submodule.span_le]
exact Submodule.subset_span⟩⟩