English
If 0 ∈ t and for all a with ‖a‖≤1 we have a•s ⊆ t, then s ⊆ balancedCore 𝕜 t.
Русский
Пусть 0 ∈ t и для всех a с ‖a‖≤1 выполнено a•s ⊆ t; тогда s ⊆ balancedCore 𝕜 t.
LaTeX
$$(ht : 0 \\in t) \\land (hst : ∀ a:𝕜, \\|a\\| ≤ 1 → a\\cdot s ⊆ t) ⇒ s ⊆ balancedCore 𝕜 t$$
Lean4
theorem subset_balancedCore (ht : (0 : E) ∈ t) (hst : ∀ a : 𝕜, ‖a‖ ≤ 1 → a • s ⊆ t) : s ⊆ balancedCore 𝕜 t :=
by
rw [balancedCore_eq_iInter ht]
refine subset_iInter₂ fun a ha ↦ ?_
rw [subset_smul_set_iff₀ (norm_pos_iff.mp <| zero_lt_one.trans_le ha)]
apply hst
rw [norm_inv]
exact inv_le_one_of_one_le₀ ha