Module: Mathlib.NumberTheory.AbelSummation

Goal state before:
pp: case inr.hab
𝕜 : Type u_1
inst✝ : RCLike 𝕜
c : ℕ → 𝕜
f : ℝ → 𝕜
a b : ℝ
ha : 0 ≤ a
hab : a ≤ b
hf_diff : ∀ t ∈ Set.Icc a b, DifferentiableAt ℝ f t
hf_int : IntegrableOn (deriv f) (Set.Icc a b) volume
aux1 : ↑⌊a⌋₊ ≤ a
aux2 : b ≤ ↑⌊b⌋₊ + 1
hb : ⌊a⌋₊ < ⌊b⌋₊
aux3 : a ≤ ↑⌊a⌋₊ + 1
aux4 : ↑⌊a⌋₊ + 1 ≤ b
aux5 : ↑⌊b⌋₊ ≤ b
aux6 : a ≤ ↑⌊b⌋₊
this :
  ∑ k ∈ Ioc ⌊a⌋₊ (⌊b⌋₊ - 1), (f ↑(k + 1) - f ↑k) * ∑ n ∈ Icc 0 k, c n =
    ∑ k ∈ Ico (⌊a⌋₊ + 1) ⌊b⌋₊, ∫ (t : ℝ) in ↑k..↑(k + 1), deriv f t * ∑ n ∈ Icc 0 ⌊t⌋₊, c n
⊢ IntervalIntegrable (fun x ↦ deriv f x * ∑ n ∈ Icc 0 ⌊x⌋₊, c n) volume a ↑⌊b⌋₊

pp: case inr.hac
𝕜 : Type u_1
inst✝ : RCLike 𝕜
c : ℕ → 𝕜
f : ℝ → 𝕜
a b : ℝ
ha : 0 ≤ a
hab : a ≤ b
hf_diff : ∀ t ∈ Set.Icc a b, DifferentiableAt ℝ f t
hf_int : IntegrableOn (deriv f) (Set.Icc a b) volume
aux1 : ↑⌊a⌋₊ ≤ a
aux2 : b ≤ ↑⌊b⌋₊ + 1
hb : ⌊a⌋₊ < ⌊b⌋₊
aux3 : a ≤ ↑⌊a⌋₊ + 1
aux4 : ↑⌊a⌋₊ + 1 ≤ b
aux5 : ↑⌊b⌋₊ ≤ b
aux6 : a ≤ ↑⌊b⌋₊
this :
  ∑ k ∈ Ioc ⌊a⌋₊ (⌊b⌋₊ - 1), (f ↑(k + 1) - f ↑k) * ∑ n ∈ Icc 0 k, c n =
    ∑ k ∈ Ico (⌊a⌋₊ + 1) ⌊b⌋₊, ∫ (t : ℝ) in ↑k..↑(k + 1), deriv f t * ∑ n ∈ Icc 0 ⌊t⌋₊, c n
⊢ IntervalIntegrable (fun x ↦ deriv f x * ∑ n ∈ Icc 0 ⌊x⌋₊, c n) volume a (↑⌊a⌋₊ + 1)

pp: case inr
𝕜 : Type u_1
inst✝ : RCLike 𝕜
c : ℕ → 𝕜
f : ℝ → 𝕜
a b : ℝ
ha : 0 ≤ a
hab : a ≤ b
hf_diff : ∀ t ∈ Set.Icc a b, DifferentiableAt ℝ f t
hf_int : IntegrableOn (deriv f) (Set.Icc a b) volume
aux1 : ↑⌊a⌋₊ ≤ a
aux2 : b ≤ ↑⌊b⌋₊ + 1
hb : ⌊a⌋₊ < ⌊b⌋₊
aux3 : a ≤ ↑⌊a⌋₊ + 1
aux4 : ↑⌊a⌋₊ + 1 ≤ b
aux5 : ↑⌊b⌋₊ ≤ b
aux6 : a ≤ ↑⌊b⌋₊
this :
  ∑ k ∈ Ioc ⌊a⌋₊ (⌊b⌋₊ - 1), (f ↑(k + 1) - f ↑k) * ∑ n ∈ Icc 0 k, c n =
    ∑ k ∈ Ico (⌊a⌋₊ + 1) ⌊b⌋₊, ∫ (t : ℝ) in ↑k..↑(k + 1), deriv f t * ∑ n ∈ Icc 0 ⌊t⌋₊, c n
⊢ ∀ k ∈ Set.Ico ⌊a⌋₊.succ ⌊b⌋₊, IntervalIntegrable (fun t ↦ deriv f t * ∑ n ∈ Icc 0 ⌊t⌋₊, c n) volume ↑k ↑(k + 1)

Tactic:
· rw [intervalIntegrable_iff_integrableOn_Icc_of_le aux6]
    exact (integrableOn_mul_sum_Icc c ha hf_int).mono_set (Set.Icc_subset_Icc_right aux5)

Goal state after:
case inr.hac
𝕜 : Type u_1
inst✝ : RCLike 𝕜
c : ℕ → 𝕜
f : ℝ → 𝕜
a b : ℝ
ha : 0 ≤ a
hab : a ≤ b
hf_diff : ∀ t ∈ Set.Icc a b, DifferentiableAt ℝ f t
hf_int : IntegrableOn (deriv f) (Set.Icc a b) volume
aux1 : ↑⌊a⌋₊ ≤ a
aux2 : b ≤ ↑⌊b⌋₊ + 1
hb : ⌊a⌋₊ < ⌊b⌋₊
aux3 : a ≤ ↑⌊a⌋₊ + 1
aux4 : ↑⌊a⌋₊ + 1 ≤ b
aux5 : ↑⌊b⌋₊ ≤ b
aux6 : a ≤ ↑⌊b⌋₊
this :
  ∑ k ∈ Ioc ⌊a⌋₊ (⌊b⌋₊ - 1), (f ↑(k + 1) - f ↑k) * ∑ n ∈ Icc 0 k, c n =
    ∑ k ∈ Ico (⌊a⌋₊ + 1) ⌊b⌋₊, ∫ (t : ℝ) in ↑k..↑(k + 1), deriv f t * ∑ n ∈ Icc 0 ⌊t⌋₊, c n
⊢ IntervalIntegrable (fun x ↦ deriv f x * ∑ n ∈ Icc 0 ⌊x⌋₊, c n) volume a (↑⌊a⌋₊ + 1)

case inr
𝕜 : Type u_1
inst✝ : RCLike 𝕜
c : ℕ → 𝕜
f : ℝ → 𝕜
a b : ℝ
ha : 0 ≤ a
hab : a ≤ b
hf_diff : ∀ t ∈ Set.Icc a b, DifferentiableAt ℝ f t
hf_int : IntegrableOn (deriv f) (Set.Icc a b) volume
aux1 : ↑⌊a⌋₊ ≤ a
aux2 : b ≤ ↑⌊b⌋₊ + 1
hb : ⌊a⌋₊ < ⌊b⌋₊
aux3 : a ≤ ↑⌊a⌋₊ + 1
aux4 : ↑⌊a⌋₊ + 1 ≤ b
aux5 : ↑⌊b⌋₊ ≤ b
aux6 : a ≤ ↑⌊b⌋₊
this :
  ∑ k ∈ Ioc ⌊a⌋₊ (⌊b⌋₊ - 1), (f ↑(k + 1) - f ↑k) * ∑ n ∈ Icc 0 k, c n =
    ∑ k ∈ Ico (⌊a⌋₊ + 1) ⌊b⌋₊, ∫ (t : ℝ) in ↑k..↑(k + 1), deriv f t * ∑ n ∈ Icc 0 ⌊t⌋₊, c n
⊢ ∀ k ∈ Set.Ico ⌊a⌋₊.succ ⌊b⌋₊, IntervalIntegrable (fun t ↦ deriv f t * ∑ n ∈ Icc 0 ⌊t⌋₊, c n) volume ↑k ↑(k + 1)