-- Mathlib/Analysis/Complex/PhragmenLindelof.lean
theorem quadrant_I (hd : DiffContOnCl ℂ f (Ioi 0 ×ℂ Ioi 0))
    (hB : ∃ c < (2 : ℝ), ∃ B,
      f =O[cobounded ℂ ⊓ 𝓟 (Ioi 0 ×ℂ Ioi 0)] fun z => expR (B * ‖z‖ ^ c))
    (hre : ∀ x : ℝ, 0 ≤ x → ‖f x‖ ≤ C) (him : ∀ x : ℝ, 0 ≤ x → ‖f (x * I)‖ ≤ C) (hz_re : 0 ≤ z.re)
    (hz_im : 0 ≤ z.im) : ‖f z‖ ≤ C

Proof state:
case inr.intro.intro.refine_1.intro.intro.intro.refine_1
E : Type u_1
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℂ E
C : ℝ
f : ℂ → E
hd : DiffContOnCl ℂ f (Ioi 0 ×ℂ Ioi 0)
hre : ∀ (x : ℝ), 0 ≤ x → ‖f ↑x‖ ≤ C
him : ∀ (x : ℝ), 0 ≤ x → ‖f (↑x * I)‖ ≤ C
ζ : ℂ
hζ : ζ.im ∈ Icc 0 (π / 2)
hz_re : 0 ≤ (cexp ζ).re
hz_im : 0 ≤ (cexp ζ).im
hzne : cexp ζ ≠ 0
H : MapsTo cexp (im ⁻¹' Ioo 0 (π / 2)) (Ioi 0 ×ℂ Ioi 0)
c : ℝ
hc✝ : c < 2
B : ℝ
hO : f =O[cobounded ℂ ⊓ 𝓟 (Ioi 0 ×ℂ Ioi 0)] fun z => expR (B * ‖z‖ ^ c)
hc : ContinuousWithinAt f (Ioi 0 ×ℂ Ioi 0) 0
w : ℂ
⊢ 0 ≤ (B ⊔ 0) * expR (c * |w.re|)

Tactic:
positivity

Result:
no goals

Proof state:
case inr.intro.intro.refine_3
E : Type u_1
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℂ E
C : ℝ
f : ℂ → E
hd : DiffContOnCl ℂ f (Ioi 0 ×ℂ Ioi 0)
hB : ∃ c < 2, ∃ B, f =O[cobounded ℂ ⊓ 𝓟 (Ioi 0 ×ℂ Ioi 0)] fun z => expR (B * ‖z‖ ^ c)
hre : ∀ (x : ℝ), 0 ≤ x → ‖f ↑x‖ ≤ C
him : ∀ (x : ℝ), 0 ≤ x → ‖f (↑x * I)‖ ≤ C
ζ✝ : ℂ
hζ✝ : ζ✝.im ∈ Icc 0 (π / 2)
hz_re : 0 ≤ (cexp ζ✝).re
hz_im : 0 ≤ (cexp ζ✝).im
hzne : cexp ζ✝ ≠ 0
H : MapsTo cexp (im ⁻¹' Ioo 0 (π / 2)) (Ioi 0 ×ℂ Ioi 0)
ζ : ℂ
hζ : ζ.im = π / 2
⊢ ‖(f ∘ cexp) ζ‖ ≤ C

Tactic:
rw [← re_add_im ζ, hζ, comp_apply, exp_add_mul_I, ← ofReal_cos, ← ofReal_sin,
  Real.cos_pi_div_two, Real.sin_pi_div_two, ofReal_zero, ofReal_one, one_mul, zero_add, ←
  ofReal_exp]

Result:
case inr.intro.intro.refine_3
E : Type u_1
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℂ E
C : ℝ
f : ℂ → E
hd : DiffContOnCl ℂ f (Ioi 0 ×ℂ Ioi 0)
hB : ∃ c < 2, ∃ B, f =O[cobounded ℂ ⊓ 𝓟 (Ioi 0 ×ℂ Ioi 0)] fun z => expR (B * ‖z‖ ^ c)
hre : ∀ (x : ℝ), 0 ≤ x → ‖f ↑x‖ ≤ C
him : ∀ (x : ℝ), 0 ≤ x → ‖f (↑x * I)‖ ≤ C
ζ✝ : ℂ
hζ✝ : ζ✝.im ∈ Icc 0 (π / 2)
hz_re : 0 ≤ (cexp ζ✝).re
hz_im : 0 ≤ (cexp ζ✝).im
hzne : cexp ζ✝ ≠ 0
H : MapsTo cexp (im ⁻¹' Ioo 0 (π / 2)) (Ioi 0 ×ℂ Ioi 0)
ζ : ℂ
hζ : ζ.im = π / 2
⊢ ‖f (↑(expR ζ.re) * I)‖ ≤ C

Proof state:
E : Type u_1
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℂ E
C : ℝ
f : ℂ → E
hd : DiffContOnCl ℂ f (Ioi 0 ×ℂ Ioi 0)
hB : ∃ c < 2, ∃ B, f =O[cobounded ℂ ⊓ 𝓟 (Ioi 0 ×ℂ Ioi 0)] fun z => expR (B * ‖z‖ ^ c)
hre : ∀ (x : ℝ), 0 ≤ x → ‖f ↑x‖ ≤ C
him : ∀ (x : ℝ), 0 ≤ x → ‖f (↑x * I)‖ ≤ C
ζ : ℂ
hζ : ζ.im ∈ Icc 0 (π / 2)
hz_re : 0 ≤ (cexp ζ).re
hz_im : 0 ≤ (cexp ζ).im
hzne : cexp ζ ≠ 0
z : ℂ
hz : z ∈ im ⁻¹' Ioo 0 (π / 2)
this : 0 < Real.cos z.im
⊢ 0 < expR z.re * Real.cos z.im ∧ 0 < expR z.re * Real.sin z.im

Tactic:
have : 0 < Real.sin z.im :=
  Real.sin_pos_of_mem_Ioo ⟨hz.1, hz.2.trans (half_lt_self Real.pi_pos)⟩

Result:
E : Type u_1
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℂ E
C : ℝ
f : ℂ → E
hd : DiffContOnCl ℂ f (Ioi 0 ×ℂ Ioi 0)
hB : ∃ c < 2, ∃ B, f =O[cobounded ℂ ⊓ 𝓟 (Ioi 0 ×ℂ Ioi 0)] fun z => expR (B * ‖z‖ ^ c)
hre : ∀ (x : ℝ), 0 ≤ x → ‖f ↑x‖ ≤ C
him : ∀ (x : ℝ), 0 ≤ x → ‖f (↑x * I)‖ ≤ C
ζ : ℂ
hζ : ζ.im ∈ Icc 0 (π / 2)
hz_re : 0 ≤ (cexp ζ).re
hz_im : 0 ≤ (cexp ζ).im
hzne : cexp ζ ≠ 0
z : ℂ
hz : z ∈ im ⁻¹' Ioo 0 (π / 2)
this✝ : 0 < Real.cos z.im
this : 0 < Real.sin z.im
⊢ 0 < expR z.re * Real.cos z.im ∧ 0 < expR z.re * Real.sin z.im

Proof state:
E : Type u_1
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℂ E
C : ℝ
f : ℂ → E
hd : DiffContOnCl ℂ f (Ioi 0 ×ℂ Ioi 0)
hre : ∀ (x : ℝ), 0 ≤ x → ‖f ↑x‖ ≤ C
him : ∀ (x : ℝ), 0 ≤ x → ‖f (↑x * I)‖ ≤ C
ζ : ℂ
hζ : ζ.im ∈ Icc 0 (π / 2)
hz_re : 0 ≤ (cexp ζ).re
hz_im : 0 ≤ (cexp ζ).im
hzne : cexp ζ ≠ 0
H : MapsTo cexp (im ⁻¹' Ioo 0 (π / 2)) (Ioi 0 ×ℂ Ioi 0)
c : ℝ
hc : c < 2
B : ℝ
hO : f =O[cobounded ℂ ⊓ 𝓟 (Ioi 0 ×ℂ Ioi 0)] fun z => expR (B * ‖z‖ ^ c)
⊢ 0 ∈ closure (Ioi 0 ×ℂ Ioi 0)

Tactic:
simp [closure_reProdIm, mem_reProdIm]

Result:
no goals

Proof state:
case inr.intro.intro.refine_3
E : Type u_1
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℂ E
C : ℝ
f : ℂ → E
hd : DiffContOnCl ℂ f (Ioi 0 ×ℂ Ioi 0)
hB : ∃ c < 2, ∃ B, f =O[cobounded ℂ ⊓ 𝓟 (Ioi 0 ×ℂ Ioi 0)] fun z => expR (B * ‖z‖ ^ c)
hre : ∀ (x : ℝ), 0 ≤ x → ‖f ↑x‖ ≤ C
him : ∀ (x : ℝ), 0 ≤ x → ‖f (↑x * I)‖ ≤ C
ζ : ℂ
hζ : ζ.im ∈ Icc 0 (π / 2)
hz_re : 0 ≤ (cexp ζ).re
hz_im : 0 ≤ (cexp ζ).im
hzne : cexp ζ ≠ 0
H : MapsTo cexp (im ⁻¹' Ioo 0 (π / 2)) (Ioi 0 ×ℂ Ioi 0)
⊢ ∀ (z : ℂ), z.im = π / 2 → ‖(f ∘ cexp) z‖ ≤ C

Tactic:
intro ζ hζ

Result:
case inr.intro.intro.refine_3
E : Type u_1
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℂ E
C : ℝ
f : ℂ → E
hd : DiffContOnCl ℂ f (Ioi 0 ×ℂ Ioi 0)
hB : ∃ c < 2, ∃ B, f =O[cobounded ℂ ⊓ 𝓟 (Ioi 0 ×ℂ Ioi 0)] fun z => expR (B * ‖z‖ ^ c)
hre : ∀ (x : ℝ), 0 ≤ x → ‖f ↑x‖ ≤ C
him : ∀ (x : ℝ), 0 ≤ x → ‖f (↑x * I)‖ ≤ C
ζ✝ : ℂ
hζ✝ : ζ✝.im ∈ Icc 0 (π / 2)
hz_re : 0 ≤ (cexp ζ✝).re
hz_im : 0 ≤ (cexp ζ✝).im
hzne : cexp ζ✝ ≠ 0
H : MapsTo cexp (im ⁻¹' Ioo 0 (π / 2)) (Ioi 0 ×ℂ Ioi 0)
ζ : ℂ
hζ : ζ.im = π / 2
⊢ ‖(f ∘ cexp) ζ‖ ≤ C

Proof state:
case inr.intro.intro.refine_2.intro
E : Type u_1
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℂ E
C : ℝ
f : ℂ → E
hd : DiffContOnCl ℂ f (Ioi 0 ×ℂ Ioi 0)
hB : ∃ c < 2, ∃ B, f =O[cobounded ℂ ⊓ 𝓟 (Ioi 0 ×ℂ Ioi 0)] fun z => expR (B * ‖z‖ ^ c)
hre : ∀ (x : ℝ), 0 ≤ x → ‖f ↑x‖ ≤ C
him : ∀ (x : ℝ), 0 ≤ x → ‖f (↑x * I)‖ ≤ C
ζ✝ : ℂ
hz_re : 0 ≤ (cexp ζ✝).re
hz_im : 0 ≤ (cexp ζ✝).im
hzne : cexp ζ✝ ≠ 0
H : MapsTo cexp (im ⁻¹' Ioo 0 (π / 2)) (Ioi 0 ×ℂ Ioi 0)
ζ : ℝ
⊢ ‖f ↑(expR ζ)‖ ≤ C

Tactic:
exact hre _ (Real.exp_pos _).le

Result:
no goals

Proof state:
case inr.intro.intro.refine_1.intro.intro.intro.refine_1
E : Type u_1
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℂ E
C : ℝ
f : ℂ → E
hd : DiffContOnCl ℂ f (Ioi 0 ×ℂ Ioi 0)
hre : ∀ (x : ℝ), 0 ≤ x → ‖f ↑x‖ ≤ C
him : ∀ (x : ℝ), 0 ≤ x → ‖f (↑x * I)‖ ≤ C
ζ : ℂ
hζ : ζ.im ∈ Icc 0 (π / 2)
hz_re : 0 ≤ (cexp ζ).re
hz_im : 0 ≤ (cexp ζ).im
hzne : cexp ζ ≠ 0
H : MapsTo cexp (im ⁻¹' Ioo 0 (π / 2)) (Ioi 0 ×ℂ Ioi 0)
c : ℝ
hc✝ : c < 2
B : ℝ
hO : f =O[cobounded ℂ ⊓ 𝓟 (Ioi 0 ×ℂ Ioi 0)] fun z => expR (B * ‖z‖ ^ c)
hc : ContinuousWithinAt f (Ioi 0 ×ℂ Ioi 0) 0
⊢ (f ∘ cexp) =O[comap re atBot ⊓ 𝓟 (im ⁻¹' Ioo 0 (π / 2))] fun z => expR ((B ⊔ 0) * expR (c * |z.re|))

Tactic:
refine ((hc.tendsto.comp <| tendsto_exp_comap_re_atBot.inf H.tendsto).isBigO_one ℝ).trans
  (isBigO_of_le _ fun w => ?_)

Result:
case inr.intro.intro.refine_1.intro.intro.intro.refine_1
E : Type u_1
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace ℂ E
C : ℝ
f : ℂ → E
hd : DiffContOnCl ℂ f (Ioi 0 ×ℂ Ioi 0)
hre : ∀ (x : ℝ), 0 ≤ x → ‖f ↑x‖ ≤ C
him : ∀ (x : ℝ), 0 ≤ x → ‖f (↑x * I)‖ ≤ C
ζ : ℂ
hζ : ζ.im ∈ Icc 0 (π / 2)
hz_re : 0 ≤ (cexp ζ).re
hz_im : 0 ≤ (cexp ζ).im
hzne : cexp ζ ≠ 0
H : MapsTo cexp (im ⁻¹' Ioo 0 (π / 2)) (Ioi 0 ×ℂ Ioi 0)
c : ℝ
hc✝ : c < 2
B : ℝ
hO : f =O[cobounded ℂ ⊓ 𝓟 (Ioi 0 ×ℂ Ioi 0)] fun z => expR (B * ‖z‖ ^ c)
hc : ContinuousWithinAt f (Ioi 0 ×ℂ Ioi 0) 0
w : ℂ
⊢ ‖1‖ ≤ ‖expR ((B ⊔ 0) * expR (c * |w.re|))‖