-- Mathlib/Analysis/Normed/Algebra/Spectrum.lean
theorem exp_mem_exp [RCLike 𝕜] [NormedRing A] [NormedAlgebra 𝕜 A] [CompleteSpace A] (a : A)
    {z : 𝕜} (hz : z ∈ spectrum 𝕜 a) : exp 𝕜 z ∈ spectrum 𝕜 (exp 𝕜 a)

Proof state:
𝕜 : Type u_1
A : Type u_2
inst✝³ : RCLike 𝕜
inst✝² : NormedRing A
inst✝¹ : NormedAlgebra 𝕜 A
inst✝ : CompleteSpace A
a : A
z : 𝕜
hz : z ∈ spectrum 𝕜 a
hexpmul : exp 𝕜 a = exp 𝕜 (a - ↑ₐ z) * ↑ₐ (exp 𝕜 z)
b : A := ∑' (n : ℕ), (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ n
⊢ ∀ᶠ (i : ℕ) in Filter.cofinite, ‖(↑(i + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ i‖ ≤ ‖a - ↑ₐ z‖ ^ i / ↑i.factorial

Tactic:
filter_upwards [Filter.eventually_cofinite_ne 0] with n hn

Result:
case h
𝕜 : Type u_1
A : Type u_2
inst✝³ : RCLike 𝕜
inst✝² : NormedRing A
inst✝¹ : NormedAlgebra 𝕜 A
inst✝ : CompleteSpace A
a : A
z : 𝕜
hz : z ∈ spectrum 𝕜 a
hexpmul : exp 𝕜 a = exp 𝕜 (a - ↑ₐ z) * ↑ₐ (exp 𝕜 z)
b : A := ∑' (n : ℕ), (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ n
n : ℕ
hn : n ≠ 0
⊢ ‖(↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ n‖ ≤ ‖a - ↑ₐ z‖ ^ n / ↑n.factorial

Proof state:
𝕜 : Type u_1
A : Type u_2
inst✝³ : RCLike 𝕜
inst✝² : NormedRing A
inst✝¹ : NormedAlgebra 𝕜 A
inst✝ : CompleteSpace A
a : A
z : 𝕜
hz : z ∈ spectrum 𝕜 a
hexpmul : exp 𝕜 a = exp 𝕜 (a - ↑ₐ z) * ↑ₐ (exp 𝕜 z)
b : A := ∑' (n : ℕ), (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ n
hb : Summable fun n => (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ n
h₀ : ∑' (n : ℕ), (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ (n + 1) = (a - ↑ₐ z) * b
⊢ ∑' (n : ℕ), (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ (n + 1) = b * (a - ↑ₐ z)

Tactic:
simpa only [pow_succ, Algebra.smul_mul_assoc] using hb.tsum_mul_right (a - ↑ₐ z)

Result:
no goals

Proof state:
𝕜 : Type u_1
A : Type u_2
inst✝³ : RCLike 𝕜
inst✝² : NormedRing A
inst✝¹ : NormedAlgebra 𝕜 A
inst✝ : CompleteSpace A
a : A
z : 𝕜
hz : z ∈ spectrum 𝕜 a
hexpmul : exp 𝕜 a = exp 𝕜 (a - ↑ₐ z) * ↑ₐ (exp 𝕜 z)
⊢ exp 𝕜 z ∈ spectrum 𝕜 (exp 𝕜 a)

Tactic:
let b := ∑' n : ℕ, ((n + 1).factorial⁻¹ : 𝕜) • (a - ↑ₐ z) ^ n

Result:
𝕜 : Type u_1
A : Type u_2
inst✝³ : RCLike 𝕜
inst✝² : NormedRing A
inst✝¹ : NormedAlgebra 𝕜 A
inst✝ : CompleteSpace A
a : A
z : 𝕜
hz : z ∈ spectrum 𝕜 a
hexpmul : exp 𝕜 a = exp 𝕜 (a - ↑ₐ z) * ↑ₐ (exp 𝕜 z)
b : A := ∑' (n : ℕ), (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ n
⊢ exp 𝕜 z ∈ spectrum 𝕜 (exp 𝕜 a)

Proof state:
𝕜 : Type u_1
A : Type u_2
inst✝³ : RCLike 𝕜
inst✝² : NormedRing A
inst✝¹ : NormedAlgebra 𝕜 A
inst✝ : CompleteSpace A
a : A
z : 𝕜
hz : z ∈ spectrum 𝕜 a
hexpmul : exp 𝕜 a = exp 𝕜 (a - ↑ₐ z) * ↑ₐ (exp 𝕜 z)
b : A := ∑' (n : ℕ), (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ n
hb : Summable fun n => (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ n
h₀ : ∑' (n : ℕ), (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ (n + 1) = (a - ↑ₐ z) * b
⊢ exp 𝕜 z ∈ spectrum 𝕜 (exp 𝕜 a)

Tactic:
have h₁ : (∑' n : ℕ, ((n + 1).factorial⁻¹ : 𝕜) • (a - ↑ₐ z) ^ (n + 1)) = b * (a - ↑ₐ z) := by
  simpa only [pow_succ, Algebra.smul_mul_assoc] using hb.tsum_mul_right (a - ↑ₐ z)

Result:
𝕜 : Type u_1
A : Type u_2
inst✝³ : RCLike 𝕜
inst✝² : NormedRing A
inst✝¹ : NormedAlgebra 𝕜 A
inst✝ : CompleteSpace A
a : A
z : 𝕜
hz : z ∈ spectrum 𝕜 a
hexpmul : exp 𝕜 a = exp 𝕜 (a - ↑ₐ z) * ↑ₐ (exp 𝕜 z)
b : A := ∑' (n : ℕ), (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ n
hb : Summable fun n => (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ n
h₀ : ∑' (n : ℕ), (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ (n + 1) = (a - ↑ₐ z) * b
h₁ : ∑' (n : ℕ), (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ (n + 1) = b * (a - ↑ₐ z)
⊢ exp 𝕜 z ∈ spectrum 𝕜 (exp 𝕜 a)

Proof state:
𝕜 : Type u_1
A : Type u_2
inst✝³ : RCLike 𝕜
inst✝² : NormedRing A
inst✝¹ : NormedAlgebra 𝕜 A
inst✝ : CompleteSpace A
a : A
z : 𝕜
hz : z ∈ spectrum 𝕜 a
hexpmul : exp 𝕜 a = exp 𝕜 (a - ↑ₐ z) * ↑ₐ (exp 𝕜 z)
b : A := ∑' (n : ℕ), (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ n
hb : Summable fun n => (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ n
⊢ exp 𝕜 z ∈ spectrum 𝕜 (exp 𝕜 a)

Tactic:
have h₀ : (∑' n : ℕ, ((n + 1).factorial⁻¹ : 𝕜) • (a - ↑ₐ z) ^ (n + 1)) = (a - ↑ₐ z) * b := by
  simpa only [mul_smul_comm, pow_succ'] using hb.tsum_mul_left (a - ↑ₐ z)

Result:
𝕜 : Type u_1
A : Type u_2
inst✝³ : RCLike 𝕜
inst✝² : NormedRing A
inst✝¹ : NormedAlgebra 𝕜 A
inst✝ : CompleteSpace A
a : A
z : 𝕜
hz : z ∈ spectrum 𝕜 a
hexpmul : exp 𝕜 a = exp 𝕜 (a - ↑ₐ z) * ↑ₐ (exp 𝕜 z)
b : A := ∑' (n : ℕ), (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ n
hb : Summable fun n => (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ n
h₀ : ∑' (n : ℕ), (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ (n + 1) = (a - ↑ₐ z) * b
⊢ exp 𝕜 z ∈ spectrum 𝕜 (exp 𝕜 a)

Proof state:
𝕜 : Type u_1
A : Type u_2
inst✝³ : RCLike 𝕜
inst✝² : NormedRing A
inst✝¹ : NormedAlgebra 𝕜 A
inst✝ : CompleteSpace A
a : A
z : 𝕜
hz : z ∈ spectrum 𝕜 a
hexpmul : exp 𝕜 a = exp 𝕜 (a - ↑ₐ z) * ↑ₐ (exp 𝕜 z)
b : A := ∑' (n : ℕ), (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ n
⊢ Summable fun n => (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ n

Tactic:
refine .of_norm_bounded_eventually _ (Real.summable_pow_div_factorial ‖a - ↑ₐ z‖) ?_

Result:
𝕜 : Type u_1
A : Type u_2
inst✝³ : RCLike 𝕜
inst✝² : NormedRing A
inst✝¹ : NormedAlgebra 𝕜 A
inst✝ : CompleteSpace A
a : A
z : 𝕜
hz : z ∈ spectrum 𝕜 a
hexpmul : exp 𝕜 a = exp 𝕜 (a - ↑ₐ z) * ↑ₐ (exp 𝕜 z)
b : A := ∑' (n : ℕ), (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ n
⊢ ∀ᶠ (i : ℕ) in Filter.cofinite, ‖(↑(i + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ i‖ ≤ ‖a - ↑ₐ z‖ ^ i / ↑i.factorial

Proof state:
case h.e'_3.h.e'_5
𝕜 : Type u_1
A : Type u_2
inst✝³ : RCLike 𝕜
inst✝² : NormedRing A
inst✝¹ : NormedAlgebra 𝕜 A
inst✝ : CompleteSpace A
a : A
z : 𝕜
hz : z ∈ spectrum 𝕜 a
hexpmul : exp 𝕜 a = exp 𝕜 (a - ↑ₐ z) * ↑ₐ (exp 𝕜 z)
b : A := ∑' (n : ℕ), (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ n
hb : Summable fun n => (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ n
h₀ : ∑' (n : ℕ), (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ (n + 1) = (a - ↑ₐ z) * b
h₁ : ∑' (n : ℕ), (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ (n + 1) = b * (a - ↑ₐ z)
⊢ 1 = (↑(Nat.factorial 0))⁻¹ • (a - ↑ₐ z) ^ 0

Tactic:
simp only [Nat.factorial_zero, Nat.cast_one, inv_one, pow_zero, one_smul]

Result:
no goals

Proof state:
case h
𝕜 : Type u_1
A : Type u_2
inst✝³ : RCLike 𝕜
inst✝² : NormedRing A
inst✝¹ : NormedAlgebra 𝕜 A
inst✝ : CompleteSpace A
a : A
z : 𝕜
hz : z ∈ spectrum 𝕜 a
hexpmul : exp 𝕜 a = exp 𝕜 (a - ↑ₐ z) * ↑ₐ (exp 𝕜 z)
b : A := ∑' (n : ℕ), (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ n
n : ℕ
hn : n ≠ 0
⊢ ‖(a - ↑ₐ z) ^ n‖ / ↑(n + 1).factorial ≤ ‖a - ↑ₐ z‖ ^ n / ↑n.factorial

Tactic:
exact div_le_div₀ (pow_nonneg (norm_nonneg _) n) (norm_pow_le' (a - ↑ₐ z) (zero_lt_iff.mpr hn))
  (mod_cast Nat.factorial_pos n) (mod_cast Nat.factorial_le (lt_add_one n).le)

Result:
no goals

Proof state:
𝕜 : Type u_1
A : Type u_2
inst✝³ : RCLike 𝕜
inst✝² : NormedRing A
inst✝¹ : NormedAlgebra 𝕜 A
inst✝ : CompleteSpace A
a : A
z : 𝕜
hz : z ∈ spectrum 𝕜 a
hexpmul : exp 𝕜 a = exp 𝕜 (a - ↑ₐ z) * ↑ₐ (exp 𝕜 z)
b : A := ∑' (n : ℕ), (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ n
hb : Summable fun n => (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ n
h₀ : ∑' (n : ℕ), (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ (n + 1) = (a - ↑ₐ z) * b
h₁ : ∑' (n : ℕ), (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ (n + 1) = b * (a - ↑ₐ z)
h₃ : exp 𝕜 (a - ↑ₐ z) = 1 + (a - ↑ₐ z) * b
⊢ exp 𝕜 z ∈ spectrum 𝕜 (exp 𝕜 a)

Tactic:
rw [spectrum.mem_iff, IsUnit.sub_iff, ← one_mul (↑ₐ (exp 𝕜 z)), hexpmul, ← _root_.sub_mul,
  Commute.isUnit_mul_iff (Algebra.commutes (exp 𝕜 z) (exp 𝕜 (a - ↑ₐ z) - 1)).symm,
  sub_eq_iff_eq_add'.mpr h₃, Commute.isUnit_mul_iff (h₀ ▸ h₁ : (a - ↑ₐ z) * b = b * (a - ↑ₐ z))]

Result:
𝕜 : Type u_1
A : Type u_2
inst✝³ : RCLike 𝕜
inst✝² : NormedRing A
inst✝¹ : NormedAlgebra 𝕜 A
inst✝ : CompleteSpace A
a : A
z : 𝕜
hz : z ∈ spectrum 𝕜 a
hexpmul : exp 𝕜 a = exp 𝕜 (a - ↑ₐ z) * ↑ₐ (exp 𝕜 z)
b : A := ∑' (n : ℕ), (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ n
hb : Summable fun n => (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ n
h₀ : ∑' (n : ℕ), (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ (n + 1) = (a - ↑ₐ z) * b
h₁ : ∑' (n : ℕ), (↑(n + 1).factorial)⁻¹ • (a - ↑ₐ z) ^ (n + 1) = b * (a - ↑ₐ z)
h₃ : exp 𝕜 (a - ↑ₐ z) = 1 + (a - ↑ₐ z) * b
⊢ ¬((IsUnit (a - ↑ₐ z) ∧ IsUnit b) ∧ IsUnit (↑ₐ (exp 𝕜 z)))