Theorem: sum_bernoulli
File: Mathlib/NumberTheory/Bernoulli.lean

Proof steps:
state_before: A : Type u_1
inst✝¹ : CommRing A
inst✝ : Algebra ℚ A
n : ℕ
⊢ ∑ k ∈ range n, ↑(n.choose k) * bernoulli k = if n = 1 then 1 else 0
state_after: case zero
A : Type u_1
inst✝¹ : CommRing A
inst✝ : Algebra ℚ A
⊢ ∑ k ∈ range 0, ↑(Nat.choose 0 k) * bernoulli k = if 0 = 1 then 1 else 0

case succ
A : Type u_1
inst✝¹ : CommRing A
inst✝ : Algebra ℚ A
n : ℕ
⊢ ∑ k ∈ range (n + 1), ↑((n + 1).choose k) * bernoulli k = if n + 1 = 1 then 1 else 0
tactic: cases' n with n
state_before: case succ
A : Type u_1
inst✝¹ : CommRing A
inst✝ : Algebra ℚ A
n : ℕ
⊢ ∑ k ∈ range (n + 1), ↑((n + 1).choose k) * bernoulli k = if n + 1 = 1 then 1 else 0
state_after: case succ.zero
A : Type u_1
inst✝¹ : CommRing A
inst✝ : Algebra ℚ A
⊢ ∑ k ∈ range (0 + 1), ↑((0 + 1).choose k) * bernoulli k = if 0 + 1 = 1 then 1 else 0

case succ.succ
A : Type u_1
inst✝¹ : CommRing A
inst✝ : Algebra ℚ A
n : ℕ
⊢ ∑ k ∈ range (n + 1 + 1), ↑((n + 1 + 1).choose k) * bernoulli k = if n + 1 + 1 = 1 then 1 else 0
tactic: cases' n with n
state_before: case succ.succ
A : Type u_1
inst✝¹ : CommRing A
inst✝ : Algebra ℚ A
n : ℕ
⊢ ∑ k ∈ range (n + 1 + 1), ↑((n + 1 + 1).choose k) * bernoulli k = if n + 1 + 1 = 1 then 1 else 0
state_after: case succ.succ
A : Type u_1
inst✝¹ : CommRing A
inst✝ : Algebra ℚ A
n : ℕ
⊢ ∑ i ∈ range n, ↑((n + 2).choose (i + 2)) * bernoulli (i + 2) = ↑n / 2
tactic: suffices (∑ i ∈ range n, ↑((n + 2).choose (i + 2)) * bernoulli (i + 2)) = n / 2 by
    simp only [this, sum_range_succ', cast_succ, bernoulli_one, bernoulli_zero, choose_one_right,
      mul_one, choose_zero_right, cast_zero, if_false, zero_add, succ_succ_ne_one]
    ring
state_before: case succ.succ
A : Type u_1
inst✝¹ : CommRing A
inst✝ : Algebra ℚ A
n : ℕ
⊢ ∑ i ∈ range n, ↑((n + 2).choose (i + 2)) * bernoulli (i + 2) = ↑n / 2
state_after: case succ.succ
A : Type u_1
inst✝¹ : CommRing A
inst✝ : Algebra ℚ A
n : ℕ
f : ∑ k ∈ range n.succ.succ, ↑(n.succ.succ.choose k) * bernoulli' k = ↑n.succ.succ
⊢ ∑ i ∈ range n, ↑((n + 2).choose (i + 2)) * bernoulli (i + 2) = ↑n / 2
tactic: have f := sum_bernoulli' n.succ.succ
state_before: case succ.succ
A : Type u_1
inst✝¹ : CommRing A
inst✝ : Algebra ℚ A
n : ℕ
f : ∑ k ∈ range n.succ.succ, ↑(n.succ.succ.choose k) * bernoulli' k = ↑n.succ.succ
⊢ ∑ i ∈ range n, ↑((n + 2).choose (i + 2)) * bernoulli (i + 2) = ↑n / 2
state_after: case succ.succ
A : Type u_1
inst✝¹ : CommRing A
inst✝ : Algebra ℚ A
n : ℕ
f :
  ∑ k ∈ range n, ↑(n.succ.succ.choose (k + 1 + 1)) * bernoulli' (k + 1 + 1) =
    ↑n + 1 + 1 - ↑(n.succ.succ.choose 0) * bernoulli' 0 - ↑(n.succ.succ.choose (0 + 1)) * bernoulli' (0 + 1)
⊢ ∑ i ∈ range n, ↑((n + 2).choose (i + 2)) * bernoulli (i + 2) = ↑n / 2
tactic: simp_rw [sum_range_succ', cast_succ, ← eq_sub_iff_add_eq] at f
state_before: case succ.succ
A : Type u_1
inst✝¹ : CommRing A
inst✝ : Algebra ℚ A
n : ℕ
f :
  ∑ k ∈ range n, ↑(n.succ.succ.choose (k + 1 + 1)) * bernoulli' (k + 1 + 1) =
    ↑n + 1 + 1 - ↑(n.succ.succ.choose 0) * bernoulli' 0 - ↑(n.succ.succ.choose (0 + 1)) * bernoulli' (0 + 1)
⊢ ∑ i ∈ range n, ↑((n + 2).choose (i + 2)) * bernoulli (i + 2) = ↑n / 2
state_after: case succ.succ.refine_1
A : Type u_1
inst✝¹ : CommRing A
inst✝ : Algebra ℚ A
n : ℕ
f :
  ∑ k ∈ range n, ↑(n.succ.succ.choose (k + 1 + 1)) * bernoulli' (k + 1 + 1) =
    ↑n + 1 + 1 - ↑(n.succ.succ.choose 0) * bernoulli' 0 - ↑(n.succ.succ.choose (0 + 1)) * bernoulli' (0 + 1)
⊢ ∑ i ∈ range n, ↑((n + 2).choose (i + 2)) * bernoulli (i + 2) =
    ∑ k ∈ range n, ↑(n.succ.succ.choose (k + 1 + 1)) * bernoulli' (k + 1 + 1)

case succ.succ.refine_2
A : Type u_1
inst✝¹ : CommRing A
inst✝ : Algebra ℚ A
n : ℕ
f :
  ∑ k ∈ range n, ↑(n.succ.succ.choose (k + 1 + 1)) * bernoulli' (k + 1 + 1) =
    ↑n + 1 + 1 - ↑(n.succ.succ.choose 0) * bernoulli' 0 - ↑(n.succ.succ.choose (0 + 1)) * bernoulli' (0 + 1)
⊢ ↑n + 1 + 1 - ↑(n.succ.succ.choose 0) * bernoulli' 0 - ↑(n.succ.succ.choose (0 + 1)) * bernoulli' (0 + 1) = ↑n / 2
tactic: refine Eq.trans ?_ (Eq.trans f ?_)