-- Mathlib/Analysis/Analytic/OfScalars.lean
theorem ofScalars_radius_eq_inv_of_tendsto [NormOneClass E] {r : ℝ≥0} (hr : r ≠ 0)
    (hc : Tendsto (fun n ↦ ‖c n.succ‖ / ‖c n‖) atTop (𝓝 r)) :
      (ofScalars E c).radius = ofNNReal r⁻¹

Proof state:
𝕜 : Type u_1
E : Type u_2
inst✝³ : NontriviallyNormedField 𝕜
inst✝² : NormedRing E
inst✝¹ : NormedAlgebra 𝕜 E
c : ℕ → 𝕜
inst✝ : NormOneClass E
r : ℝ≥0
hr : r ≠ 0
hc : Tendsto (fun n => ‖c n.succ‖ / ‖c n‖) atTop (𝓝 ↑r)
⊢ (ofScalars E c).radius = ↑r⁻¹

Tactic:
refine le_antisymm ?_ (ofScalars_radius_ge_inv_of_tendsto E c hr hc)

Result:
𝕜 : Type u_1
E : Type u_2
inst✝³ : NontriviallyNormedField 𝕜
inst✝² : NormedRing E
inst✝¹ : NormedAlgebra 𝕜 E
c : ℕ → 𝕜
inst✝ : NormOneClass E
r : ℝ≥0
hr : r ≠ 0
hc : Tendsto (fun n => ‖c n.succ‖ / ‖c n‖) atTop (𝓝 ↑r)
⊢ (ofScalars E c).radius ≤ ↑r⁻¹

Proof state:
𝕜 : Type u_1
E : Type u_2
inst✝³ : NontriviallyNormedField 𝕜
inst✝² : NormedRing E
inst✝¹ : NormedAlgebra 𝕜 E
c : ℕ → 𝕜
inst✝ : NormOneClass E
r : ℝ≥0
hr : r ≠ 0
hc : Tendsto (fun n => ‖c n.succ‖ / ‖c n‖) atTop (𝓝 ↑r)
r' : ℝ≥0
hr' : ↑r' < (ofScalars E c).radius
this : Summable fun n => ‖ofScalars E c n‖ * ↑r' ^ n
⊢ r' * r ≤ 1

Tactic:
contrapose! this

Result:
𝕜 : Type u_1
E : Type u_2
inst✝³ : NontriviallyNormedField 𝕜
inst✝² : NormedRing E
inst✝¹ : NormedAlgebra 𝕜 E
c : ℕ → 𝕜
inst✝ : NormOneClass E
r : ℝ≥0
hr : r ≠ 0
hc : Tendsto (fun n => ‖c n.succ‖ / ‖c n‖) atTop (𝓝 ↑r)
r' : ℝ≥0
hr' : ↑r' < (ofScalars E c).radius
this : 1 < r' * r
⊢ ¬Summable fun n => ‖ofScalars E c n‖ * ↑r' ^ n

Proof state:
𝕜 : Type u_1
E : Type u_2
inst✝³ : NontriviallyNormedField 𝕜
inst✝² : NormedRing E
inst✝¹ : NormedAlgebra 𝕜 E
c : ℕ → 𝕜
inst✝ : NormOneClass E
r : ℝ≥0
hr : r ≠ 0
hc : Tendsto (fun n => ‖c n.succ‖ / ‖c n‖) atTop (𝓝 ↑r)
r' : ℝ≥0
hr' : ↑r' < (ofScalars E c).radius
⊢ ↑r' ≤ ↑r⁻¹

Tactic:
rw [coe_le_coe, NNReal.le_inv_iff_mul_le hr]

Result:
𝕜 : Type u_1
E : Type u_2
inst✝³ : NontriviallyNormedField 𝕜
inst✝² : NormedRing E
inst✝¹ : NormedAlgebra 𝕜 E
c : ℕ → 𝕜
inst✝ : NormOneClass E
r : ℝ≥0
hr : r ≠ 0
hc : Tendsto (fun n => ‖c n.succ‖ / ‖c n‖) atTop (𝓝 ↑r)
r' : ℝ≥0
hr' : ↑r' < (ofScalars E c).radius
⊢ r' * r ≤ 1

Proof state:
𝕜 : Type u_1
E : Type u_2
inst✝³ : NontriviallyNormedField 𝕜
inst✝² : NormedRing E
inst✝¹ : NormedAlgebra 𝕜 E
c : ℕ → 𝕜
inst✝ : NormOneClass E
r : ℝ≥0
hr : r ≠ 0
hc : Tendsto (fun n => ‖c n.succ‖ / ‖c n‖) atTop (𝓝 ↑r)
r' : ℝ≥0
hr' : ↑r' < (ofScalars E c).radius
this : 1 < r' * r
⊢ Tendsto (fun n => ‖‖c (n + 1)‖ * ↑r' ^ (n + 1)‖ / ‖‖c n‖ * ↑r' ^ n‖) atTop (𝓝 ↑(r' * r))

Tactic:
exact tendsto_succ_norm_div_norm c (by aesop) hc

Result:
no goals

Proof state:
𝕜 : Type u_1
E : Type u_2
inst✝³ : NontriviallyNormedField 𝕜
inst✝² : NormedRing E
inst✝¹ : NormedAlgebra 𝕜 E
c : ℕ → 𝕜
inst✝ : NormOneClass E
r : ℝ≥0
hr : r ≠ 0
hc : Tendsto (fun n => ‖c n.succ‖ / ‖c n‖) atTop (𝓝 ↑r)
r' : ℝ≥0
hr' : ↑r' < (ofScalars E c).radius
this : 1 < r' * r
⊢ r' ≠ 0

Tactic:
aesop

Result:
no goals

Proof state:
𝕜 : Type u_1
E : Type u_2
inst✝³ : NontriviallyNormedField 𝕜
inst✝² : NormedRing E
inst✝¹ : NormedAlgebra 𝕜 E
c : ℕ → 𝕜
inst✝ : NormOneClass E
r : ℝ≥0
hr : r ≠ 0
hc : Tendsto (fun n => ‖c n.succ‖ / ‖c n‖) atTop (𝓝 ↑r)
⊢ (ofScalars E c).radius ≤ ↑r⁻¹

Tactic:
refine le_of_forall_nnreal_lt (fun r' hr' ↦ ?_)

Result:
𝕜 : Type u_1
E : Type u_2
inst✝³ : NontriviallyNormedField 𝕜
inst✝² : NormedRing E
inst✝¹ : NormedAlgebra 𝕜 E
c : ℕ → 𝕜
inst✝ : NormOneClass E
r : ℝ≥0
hr : r ≠ 0
hc : Tendsto (fun n => ‖c n.succ‖ / ‖c n‖) atTop (𝓝 ↑r)
r' : ℝ≥0
hr' : ↑r' < (ofScalars E c).radius
⊢ ↑r' ≤ ↑r⁻¹

Proof state:
𝕜 : Type u_1
E : Type u_2
inst✝³ : NontriviallyNormedField 𝕜
inst✝² : NormedRing E
inst✝¹ : NormedAlgebra 𝕜 E
c : ℕ → 𝕜
inst✝ : NormOneClass E
r : ℝ≥0
hr : r ≠ 0
hc : Tendsto (fun n => ‖c n.succ‖ / ‖c n‖) atTop (𝓝 ↑r)
r' : ℝ≥0
hr' : ↑r' < (ofScalars E c).radius
⊢ r' * r ≤ 1

Tactic:
have := FormalMultilinearSeries.summable_norm_mul_pow _ hr'

Result:
𝕜 : Type u_1
E : Type u_2
inst✝³ : NontriviallyNormedField 𝕜
inst✝² : NormedRing E
inst✝¹ : NormedAlgebra 𝕜 E
c : ℕ → 𝕜
inst✝ : NormOneClass E
r : ℝ≥0
hr : r ≠ 0
hc : Tendsto (fun n => ‖c n.succ‖ / ‖c n‖) atTop (𝓝 ↑r)
r' : ℝ≥0
hr' : ↑r' < (ofScalars E c).radius
this : Summable fun n => ‖ofScalars E c n‖ * ↑r' ^ n
⊢ r' * r ≤ 1

Proof state:
𝕜 : Type u_1
E : Type u_2
inst✝³ : NontriviallyNormedField 𝕜
inst✝² : NormedRing E
inst✝¹ : NormedAlgebra 𝕜 E
c : ℕ → 𝕜
inst✝ : NormOneClass E
r : ℝ≥0
hr : r ≠ 0
hc : Tendsto (fun n => ‖c n.succ‖ / ‖c n‖) atTop (𝓝 ↑r)
r' : ℝ≥0
hr' : ↑r' < (ofScalars E c).radius
this : 1 < r' * r
⊢ Tendsto (fun n => ‖‖ofScalars E c (n + 1)‖ * ↑r' ^ (n + 1)‖ / ‖‖ofScalars E c n‖ * ↑r' ^ n‖) atTop
    (𝓝 ((fun a => ↑a) (r' * r)))

Tactic:
simp_rw [ofScalars_norm]

Result:
𝕜 : Type u_1
E : Type u_2
inst✝³ : NontriviallyNormedField 𝕜
inst✝² : NormedRing E
inst✝¹ : NormedAlgebra 𝕜 E
c : ℕ → 𝕜
inst✝ : NormOneClass E
r : ℝ≥0
hr : r ≠ 0
hc : Tendsto (fun n => ‖c n.succ‖ / ‖c n‖) atTop (𝓝 ↑r)
r' : ℝ≥0
hr' : ↑r' < (ofScalars E c).radius
this : 1 < r' * r
⊢ Tendsto (fun n => ‖‖c (n + 1)‖ * ↑r' ^ (n + 1)‖ / ‖‖c n‖ * ↑r' ^ n‖) atTop (𝓝 ↑(r' * r))

Proof state:
𝕜 : Type u_1
E : Type u_2
inst✝³ : NontriviallyNormedField 𝕜
inst✝² : NormedRing E
inst✝¹ : NormedAlgebra 𝕜 E
c : ℕ → 𝕜
inst✝ : NormOneClass E
r : ℝ≥0
hr : r ≠ 0
hc : Tendsto (fun n => ‖c n.succ‖ / ‖c n‖) atTop (𝓝 ↑r)
r' : ℝ≥0
hr' : ↑r' < (ofScalars E c).radius
this : 1 < r' * r
⊢ ¬Summable fun n => ‖ofScalars E c n‖ * ↑r' ^ n

Tactic:
apply not_summable_of_ratio_test_tendsto_gt_one this

Result:
𝕜 : Type u_1
E : Type u_2
inst✝³ : NontriviallyNormedField 𝕜
inst✝² : NormedRing E
inst✝¹ : NormedAlgebra 𝕜 E
c : ℕ → 𝕜
inst✝ : NormOneClass E
r : ℝ≥0
hr : r ≠ 0
hc : Tendsto (fun n => ‖c n.succ‖ / ‖c n‖) atTop (𝓝 ↑r)
r' : ℝ≥0
hr' : ↑r' < (ofScalars E c).radius
this : 1 < r' * r
⊢ Tendsto (fun n => ‖‖ofScalars E c (n + 1)‖ * ↑r' ^ (n + 1)‖ / ‖‖ofScalars E c n‖ * ↑r' ^ n‖) atTop
    (𝓝 ((fun a => ↑a) (r' * r)))