Theorem: TopologicalRing.of_norm
File: Mathlib/Topology/Algebra/Order/Field.lean

Proof steps:
state_before: R : Type u_1
𝕜 : Type u_2
inst✝³ : NonUnitalNonAssocRing R
inst✝² : LinearOrderedField 𝕜
inst✝¹ : TopologicalSpace R
inst✝ : TopologicalAddGroup R
norm : R → 𝕜
norm_nonneg : ∀ (x : R), 0 ≤ norm x
norm_mul_le : ∀ (x y : R), norm (x * y) ≤ norm x * norm y
nhds_basis : (𝓝 0).HasBasis (fun x => 0 < x) fun ε => {x | norm x < ε}
⊢ TopologicalRing R
state_after: R : Type u_1
𝕜 : Type u_2
inst✝³ : NonUnitalNonAssocRing R
inst✝² : LinearOrderedField 𝕜
inst✝¹ : TopologicalSpace R
inst✝ : TopologicalAddGroup R
norm : R → 𝕜
norm_nonneg : ∀ (x : R), 0 ≤ norm x
norm_mul_le : ∀ (x y : R), norm (x * y) ≤ norm x * norm y
nhds_basis : (𝓝 0).HasBasis (fun x => 0 < x) fun ε => {x | norm x < ε}
h0 : ∀ (f : R → R), ∀ c ≥ 0, (∀ (x : R), norm (f x) ≤ c * norm x) → Tendsto f (𝓝 0) (𝓝 0)
⊢ TopologicalRing R
tactic: have h0 : ∀ f : R → R, ∀ c ≥ (0 : 𝕜), (∀ x, norm (f x) ≤ c * norm x) →
      Tendsto f (𝓝 0) (𝓝 0) := by
    refine fun f c c0 hf ↦ (nhds_basis.tendsto_iff nhds_basis).2 fun ε ε0 ↦ ?_
    rcases exists_pos_mul_lt ε0 c with ⟨δ, δ0, hδ⟩
    refine ⟨δ, δ0, fun x hx ↦ (hf _).trans_lt ?_⟩
    exact (mul_le_mul_of_nonneg_left (le_of_lt hx) c0).trans_lt hδ
state_before: R : Type u_1
𝕜 : Type u_2
inst✝³ : NonUnitalNonAssocRing R
inst✝² : LinearOrderedField 𝕜
inst✝¹ : TopologicalSpace R
inst✝ : TopologicalAddGroup R
norm : R → 𝕜
norm_nonneg : ∀ (x : R), 0 ≤ norm x
norm_mul_le : ∀ (x y : R), norm (x * y) ≤ norm x * norm y
nhds_basis : (𝓝 0).HasBasis (fun x => 0 < x) fun ε => {x | norm x < ε}
h0 : ∀ (f : R → R), ∀ c ≥ 0, (∀ (x : R), norm (f x) ≤ c * norm x) → Tendsto f (𝓝 0) (𝓝 0)
⊢ TopologicalRing R
state_after: case hmul
R : Type u_1
𝕜 : Type u_2
inst✝³ : NonUnitalNonAssocRing R
inst✝² : LinearOrderedField 𝕜
inst✝¹ : TopologicalSpace R
inst✝ : TopologicalAddGroup R
norm : R → 𝕜
norm_nonneg : ∀ (x : R), 0 ≤ norm x
norm_mul_le : ∀ (x y : R), norm (x * y) ≤ norm x * norm y
nhds_basis : (𝓝 0).HasBasis (fun x => 0 < x) fun ε => {x | norm x < ε}
h0 : ∀ (f : R → R), ∀ c ≥ 0, (∀ (x : R), norm (f x) ≤ c * norm x) → Tendsto f (𝓝 0) (𝓝 0)
⊢ Tendsto (uncurry fun x x_1 => x * x_1) (𝓝 0 ×ˢ 𝓝 0) (𝓝 0)

case hmul_left
R : Type u_1
𝕜 : Type u_2
inst✝³ : NonUnitalNonAssocRing R
inst✝² : LinearOrderedField 𝕜
inst✝¹ : TopologicalSpace R
inst✝ : TopologicalAddGroup R
norm : R → 𝕜
norm_nonneg : ∀ (x : R), 0 ≤ norm x
norm_mul_le : ∀ (x y : R), norm (x * y) ≤ norm x * norm y
nhds_basis : (𝓝 0).HasBasis (fun x => 0 < x) fun ε => {x | norm x < ε}
h0 : ∀ (f : R → R), ∀ c ≥ 0, (∀ (x : R), norm (f x) ≤ c * norm x) → Tendsto f (𝓝 0) (𝓝 0)
⊢ ∀ (x₀ : R), Tendsto (fun x => x₀ * x) (𝓝 0) (𝓝 0)

case hmul_right
R : Type u_1
𝕜 : Type u_2
inst✝³ : NonUnitalNonAssocRing R
inst✝² : LinearOrderedField 𝕜
inst✝¹ : TopologicalSpace R
inst✝ : TopologicalAddGroup R
norm : R → 𝕜
norm_nonneg : ∀ (x : R), 0 ≤ norm x
norm_mul_le : ∀ (x y : R), norm (x * y) ≤ norm x * norm y
nhds_basis : (𝓝 0).HasBasis (fun x => 0 < x) fun ε => {x | norm x < ε}
h0 : ∀ (f : R → R), ∀ c ≥ 0, (∀ (x : R), norm (f x) ≤ c * norm x) → Tendsto f (𝓝 0) (𝓝 0)
⊢ ∀ (x₀ : R), Tendsto (fun x => x * x₀) (𝓝 0) (𝓝 0)
tactic: apply TopologicalRing.of_addGroup_of_nhds_zero
state_before: case hmul
R : Type u_1
𝕜 : Type u_2
inst✝³ : NonUnitalNonAssocRing R
inst✝² : LinearOrderedField 𝕜
inst✝¹ : TopologicalSpace R
inst✝ : TopologicalAddGroup R
norm : R → 𝕜
norm_nonneg : ∀ (x : R), 0 ≤ norm x
norm_mul_le : ∀ (x y : R), norm (x * y) ≤ norm x * norm y
nhds_basis : (𝓝 0).HasBasis (fun x => 0 < x) fun ε => {x | norm x < ε}
h0 : ∀ (f : R → R), ∀ c ≥ 0, (∀ (x : R), norm (f x) ≤ c * norm x) → Tendsto f (𝓝 0) (𝓝 0)
⊢ Tendsto (uncurry fun x x_1 => x * x_1) (𝓝 0 ×ˢ 𝓝 0) (𝓝 0)

case hmul_left
R : Type u_1
𝕜 : Type u_2
inst✝³ : NonUnitalNonAssocRing R
inst✝² : LinearOrderedField 𝕜
inst✝¹ : TopologicalSpace R
inst✝ : TopologicalAddGroup R
norm : R → 𝕜
norm_nonneg : ∀ (x : R), 0 ≤ norm x
norm_mul_le : ∀ (x y : R), norm (x * y) ≤ norm x * norm y
nhds_basis : (𝓝 0).HasBasis (fun x => 0 < x) fun ε => {x | norm x < ε}
h0 : ∀ (f : R → R), ∀ c ≥ 0, (∀ (x : R), norm (f x) ≤ c * norm x) → Tendsto f (𝓝 0) (𝓝 0)
⊢ ∀ (x₀ : R), Tendsto (fun x => x₀ * x) (𝓝 0) (𝓝 0)

case hmul_right
R : Type u_1
𝕜 : Type u_2
inst✝³ : NonUnitalNonAssocRing R
inst✝² : LinearOrderedField 𝕜
inst✝¹ : TopologicalSpace R
inst✝ : TopologicalAddGroup R
norm : R → 𝕜
norm_nonneg : ∀ (x : R), 0 ≤ norm x
norm_mul_le : ∀ (x y : R), norm (x * y) ≤ norm x * norm y
nhds_basis : (𝓝 0).HasBasis (fun x => 0 < x) fun ε => {x | norm x < ε}
h0 : ∀ (f : R → R), ∀ c ≥ 0, (∀ (x : R), norm (f x) ≤ c * norm x) → Tendsto f (𝓝 0) (𝓝 0)
⊢ ∀ (x₀ : R), Tendsto (fun x => x * x₀) (𝓝 0) (𝓝 0)
state_after: case hmul_left
R : Type u_1
𝕜 : Type u_2
inst✝³ : NonUnitalNonAssocRing R
inst✝² : LinearOrderedField 𝕜
inst✝¹ : TopologicalSpace R
inst✝ : TopologicalAddGroup R
norm : R → 𝕜
norm_nonneg : ∀ (x : R), 0 ≤ norm x
norm_mul_le : ∀ (x y : R), norm (x * y) ≤ norm x * norm y
nhds_basis : (𝓝 0).HasBasis (fun x => 0 < x) fun ε => {x | norm x < ε}
h0 : ∀ (f : R → R), ∀ c ≥ 0, (∀ (x : R), norm (f x) ≤ c * norm x) → Tendsto f (𝓝 0) (𝓝 0)
⊢ ∀ (x₀ : R), Tendsto (fun x => x₀ * x) (𝓝 0) (𝓝 0)

case hmul_right
R : Type u_1
𝕜 : Type u_2
inst✝³ : NonUnitalNonAssocRing R
inst✝² : LinearOrderedField 𝕜
inst✝¹ : TopologicalSpace R
inst✝ : TopologicalAddGroup R
norm : R → 𝕜
norm_nonneg : ∀ (x : R), 0 ≤ norm x
norm_mul_le : ∀ (x y : R), norm (x * y) ≤ norm x * norm y
nhds_basis : (𝓝 0).HasBasis (fun x => 0 < x) fun ε => {x | norm x < ε}
h0 : ∀ (f : R → R), ∀ c ≥ 0, (∀ (x : R), norm (f x) ≤ c * norm x) → Tendsto f (𝓝 0) (𝓝 0)
⊢ ∀ (x₀ : R), Tendsto (fun x => x * x₀) (𝓝 0) (𝓝 0)
tactic: case hmul =>
    refine ((nhds_basis.prod nhds_basis).tendsto_iff nhds_basis).2 fun ε ε0 ↦ ?_
    refine ⟨(1, ε), ⟨one_pos, ε0⟩, fun (x, y) ⟨hx, hy⟩ => ?_⟩
    simp only [sub_zero] at *
    calc norm (x * y) ≤ norm x * norm y := norm_mul_le _ _
    _ < ε := mul_lt_of_le_one_of_lt_of_nonneg hx.le hy (norm_nonneg _)
state_before: case hmul_left
R : Type u_1
𝕜 : Type u_2
inst✝³ : NonUnitalNonAssocRing R
inst✝² : LinearOrderedField 𝕜
inst✝¹ : TopologicalSpace R
inst✝ : TopologicalAddGroup R
norm : R → 𝕜
norm_nonneg : ∀ (x : R), 0 ≤ norm x
norm_mul_le : ∀ (x y : R), norm (x * y) ≤ norm x * norm y
nhds_basis : (𝓝 0).HasBasis (fun x => 0 < x) fun ε => {x | norm x < ε}
h0 : ∀ (f : R → R), ∀ c ≥ 0, (∀ (x : R), norm (f x) ≤ c * norm x) → Tendsto f (𝓝 0) (𝓝 0)
⊢ ∀ (x₀ : R), Tendsto (fun x => x₀ * x) (𝓝 0) (𝓝 0)

case hmul_right
R : Type u_1
𝕜 : Type u_2
inst✝³ : NonUnitalNonAssocRing R
inst✝² : LinearOrderedField 𝕜
inst✝¹ : TopologicalSpace R
inst✝ : TopologicalAddGroup R
norm : R → 𝕜
norm_nonneg : ∀ (x : R), 0 ≤ norm x
norm_mul_le : ∀ (x y : R), norm (x * y) ≤ norm x * norm y
nhds_basis : (𝓝 0).HasBasis (fun x => 0 < x) fun ε => {x | norm x < ε}
h0 : ∀ (f : R → R), ∀ c ≥ 0, (∀ (x : R), norm (f x) ≤ c * norm x) → Tendsto f (𝓝 0) (𝓝 0)
⊢ ∀ (x₀ : R), Tendsto (fun x => x * x₀) (𝓝 0) (𝓝 0)
state_after: case hmul_right
R : Type u_1
𝕜 : Type u_2
inst✝³ : NonUnitalNonAssocRing R
inst✝² : LinearOrderedField 𝕜
inst✝¹ : TopologicalSpace R
inst✝ : TopologicalAddGroup R
norm : R → 𝕜
norm_nonneg : ∀ (x : R), 0 ≤ norm x
norm_mul_le : ∀ (x y : R), norm (x * y) ≤ norm x * norm y
nhds_basis : (𝓝 0).HasBasis (fun x => 0 < x) fun ε => {x | norm x < ε}
h0 : ∀ (f : R → R), ∀ c ≥ 0, (∀ (x : R), norm (f x) ≤ c * norm x) → Tendsto f (𝓝 0) (𝓝 0)
⊢ ∀ (x₀ : R), Tendsto (fun x => x * x₀) (𝓝 0) (𝓝 0)
tactic: case hmul_left => exact fun x => h0 _ (norm x) (norm_nonneg _) (norm_mul_le x)