Theorem: Complex.GammaSeq_mul
File: Mathlib/Analysis/SpecialFunctions/Gamma/Beta.lean

Proof steps:
state_before: z : ℂ
n : ℕ
hn : n ≠ 0
⊢ z.GammaSeq n * (1 - z).GammaSeq n = ↑n / (↑n + 1 - z) * (1 / (z * ∏ j ∈ Finset.range n, (1 - z ^ 2 / (↑j + 1) ^ 2)))
state_after: z : ℂ
n : ℕ
hn : n ≠ 0
aux : ∀ (a b c d : ℂ), a * b * (c * d) = a * c * (b * d)
⊢ z.GammaSeq n * (1 - z).GammaSeq n = ↑n / (↑n + 1 - z) * (1 / (z * ∏ j ∈ Finset.range n, (1 - z ^ 2 / (↑j + 1) ^ 2)))
tactic: have aux : ∀ a b c d : ℂ, a * b * (c * d) = a * c * (b * d) := by intros; ring
state_before: z : ℂ
n : ℕ
hn : n ≠ 0
aux : ∀ (a b c d : ℂ), a * b * (c * d) = a * c * (b * d)
⊢ z.GammaSeq n * (1 - z).GammaSeq n = ↑n / (↑n + 1 - z) * (1 / (z * ∏ j ∈ Finset.range n, (1 - z ^ 2 / (↑j + 1) ^ 2)))
state_after: z : ℂ
n : ℕ
hn : n ≠ 0
aux : ∀ (a b c d : ℂ), a * b * (c * d) = a * c * (b * d)
⊢ ↑n ^ z * ↑n ^ (1 - z) * ↑n ! ^ 2 /
      ((∏ j ∈ Finset.range (n + 1), (z + ↑j)) * ∏ j ∈ Finset.range (n + 1), (1 - z + ↑j)) =
    ↑n / (↑n + 1 - z) * (1 / (z * ∏ j ∈ Finset.range n, (1 - z ^ 2 / (↑j + 1) ^ 2)))
tactic: rw [GammaSeq, GammaSeq, div_mul_div_comm, aux, ← pow_two]
state_before: z : ℂ
n : ℕ
hn : n ≠ 0
aux : ∀ (a b c d : ℂ), a * b * (c * d) = a * c * (b * d)
⊢ ↑n ^ z * ↑n ^ (1 - z) * ↑n ! ^ 2 /
      ((∏ j ∈ Finset.range (n + 1), (z + ↑j)) * ∏ j ∈ Finset.range (n + 1), (1 - z + ↑j)) =
    ↑n / (↑n + 1 - z) * (1 / (z * ∏ j ∈ Finset.range n, (1 - z ^ 2 / (↑j + 1) ^ 2)))
state_after: z : ℂ
n : ℕ
hn : n ≠ 0
aux : ∀ (a b c d : ℂ), a * b * (c * d) = a * c * (b * d)
this : ↑n ^ z * ↑n ^ (1 - z) = ↑n
⊢ ↑n ^ z * ↑n ^ (1 - z) * ↑n ! ^ 2 /
      ((∏ j ∈ Finset.range (n + 1), (z + ↑j)) * ∏ j ∈ Finset.range (n + 1), (1 - z + ↑j)) =
    ↑n / (↑n + 1 - z) * (1 / (z * ∏ j ∈ Finset.range n, (1 - z ^ 2 / (↑j + 1) ^ 2)))
tactic: have : (n : ℂ) ^ z * (n : ℂ) ^ (1 - z) = n := by
    rw [← cpow_add _ _ (Nat.cast_ne_zero.mpr hn), add_sub_cancel, cpow_one]
state_before: z : ℂ
n : ℕ
hn : n ≠ 0
aux : ∀ (a b c d : ℂ), a * b * (c * d) = a * c * (b * d)
this : ↑n ^ z * ↑n ^ (1 - z) = ↑n
⊢ ↑n ^ z * ↑n ^ (1 - z) * ↑n ! ^ 2 /
      ((∏ j ∈ Finset.range (n + 1), (z + ↑j)) * ∏ j ∈ Finset.range (n + 1), (1 - z + ↑j)) =
    ↑n / (↑n + 1 - z) * (1 / (z * ∏ j ∈ Finset.range n, (1 - z ^ 2 / (↑j + 1) ^ 2)))
state_after: z : ℂ
n : ℕ
hn : n ≠ 0
aux : ∀ (a b c d : ℂ), a * b * (c * d) = a * c * (b * d)
this : ↑n ^ z * ↑n ^ (1 - z) = ↑n
⊢ ↑n * ↑n ! ^ 2 / ((∏ x ∈ Finset.range n, (z + ↑(x + 1)) * (1 - z + ↑x)) * (z * (↑n + 1 - z))) =
    ↑n / (↑n + 1 - z) * (1 / (z * ∏ j ∈ Finset.range n, (1 - z ^ 2 / (↑j + 1) ^ 2)))
tactic: rw [this, Finset.prod_range_succ', Finset.prod_range_succ, aux, ← Finset.prod_mul_distrib,
    Nat.cast_zero, add_zero, add_comm (1 - z) n, ← add_sub_assoc]
state_before: z : ℂ
n : ℕ
hn : n ≠ 0
aux : ∀ (a b c d : ℂ), a * b * (c * d) = a * c * (b * d)
this : ↑n ^ z * ↑n ^ (1 - z) = ↑n
⊢ ↑n * ↑n ! ^ 2 / ((∏ x ∈ Finset.range n, (z + ↑(x + 1)) * (1 - z + ↑x)) * (z * (↑n + 1 - z))) =
    ↑n / (↑n + 1 - z) * (1 / (z * ∏ j ∈ Finset.range n, (1 - z ^ 2 / (↑j + 1) ^ 2)))
state_after: z : ℂ
n : ℕ
hn : n ≠ 0
aux : ∀ (a b c d : ℂ), a * b * (c * d) = a * c * (b * d)
this✝ : ↑n ^ z * ↑n ^ (1 - z) = ↑n
this : ∀ (j : ℕ), (z + ↑(j + 1)) * (1 - z + ↑j) = ↑((j + 1) ^ 2) * (1 - z ^ 2 / (↑j + 1) ^ 2)
⊢ ↑n * ↑n ! ^ 2 / ((∏ x ∈ Finset.range n, (z + ↑(x + 1)) * (1 - z + ↑x)) * (z * (↑n + 1 - z))) =
    ↑n / (↑n + 1 - z) * (1 / (z * ∏ j ∈ Finset.range n, (1 - z ^ 2 / (↑j + 1) ^ 2)))
tactic: have : ∀ j : ℕ, (z + ↑(j + 1)) * (↑1 - z + ↑j) =
      ((j + 1) ^ 2 :) * (↑1 - z ^ 2 / ((j : ℂ) + 1) ^ 2) := by
    intro j
    push_cast
    have : (j : ℂ) + 1 ≠ 0 := by rw [← Nat.cast_succ, Nat.cast_ne_zero]; exact Nat.succ_ne_zero j
    field_simp; ring
state_before: z : ℂ
n : ℕ
hn : n ≠ 0
aux : ∀ (a b c d : ℂ), a * b * (c * d) = a * c * (b * d)
this✝ : ↑n ^ z * ↑n ^ (1 - z) = ↑n
this : ∀ (j : ℕ), (z + ↑(j + 1)) * (1 - z + ↑j) = ↑((j + 1) ^ 2) * (1 - z ^ 2 / (↑j + 1) ^ 2)
⊢ ↑n * ↑n ! ^ 2 / ((∏ x ∈ Finset.range n, (z + ↑(x + 1)) * (1 - z + ↑x)) * (z * (↑n + 1 - z))) =
    ↑n / (↑n + 1 - z) * (1 / (z * ∏ j ∈ Finset.range n, (1 - z ^ 2 / (↑j + 1) ^ 2)))
state_after: z : ℂ
n : ℕ
hn : n ≠ 0
aux : ∀ (a b c d : ℂ), a * b * (c * d) = a * c * (b * d)
this✝ : ↑n ^ z * ↑n ^ (1 - z) = ↑n
this : ∀ (j : ℕ), (z + ↑(j + 1)) * (1 - z + ↑j) = ↑((j + 1) ^ 2) * (1 - z ^ 2 / (↑j + 1) ^ 2)
⊢ ↑n * ↑n ! ^ 2 / ((∏ x ∈ Finset.range n, ↑((x + 1) ^ 2) * (1 - z ^ 2 / (↑x + 1) ^ 2)) * (z * (↑n + 1 - z))) =
    ↑n / (↑n + 1 - z) * (1 / (z * ∏ j ∈ Finset.range n, (1 - z ^ 2 / (↑j + 1) ^ 2)))
tactic: simp_rw [this]
state_before: z : ℂ
n : ℕ
hn : n ≠ 0
aux : ∀ (a b c d : ℂ), a * b * (c * d) = a * c * (b * d)
this✝ : ↑n ^ z * ↑n ^ (1 - z) = ↑n
this : ∀ (j : ℕ), (z + ↑(j + 1)) * (1 - z + ↑j) = ↑((j + 1) ^ 2) * (1 - z ^ 2 / (↑j + 1) ^ 2)
⊢ ↑n * ↑n ! ^ 2 / ((∏ x ∈ Finset.range n, ↑((x + 1) ^ 2) * (1 - z ^ 2 / (↑x + 1) ^ 2)) * (z * (↑n + 1 - z))) =
    ↑n / (↑n + 1 - z) * (1 / (z * ∏ j ∈ Finset.range n, (1 - z ^ 2 / (↑j + 1) ^ 2)))
state_after: case hb
z : ℂ
n : ℕ
hn : n ≠ 0
aux : ∀ (a b c d : ℂ), a * b * (c * d) = a * c * (b * d)
this✝ : ↑n ^ z * ↑n ^ (1 - z) = ↑n
this : ∀ (j : ℕ), (z + ↑(j + 1)) * (1 - z + ↑j) = ↑((j + 1) ^ 2) * (1 - z ^ 2 / (↑j + 1) ^ 2)
⊢ ↑n ! ^ 2 ≠ 0
tactic: rw [Finset.prod_mul_distrib, ← Nat.cast_prod, Finset.prod_pow,
    Finset.prod_range_add_one_eq_factorial, Nat.cast_pow,
    (by intros; ring : ∀ a b c d : ℂ, a * b * (c * d) = a * (d * (b * c))), ← div_div,
    mul_div_cancel_right₀, ← div_div, mul_comm z _, mul_one_div]
state_before: case hb
z : ℂ
n : ℕ
hn : n ≠ 0
aux : ∀ (a b c d : ℂ), a * b * (c * d) = a * c * (b * d)
this✝ : ↑n ^ z * ↑n ^ (1 - z) = ↑n
this : ∀ (j : ℕ), (z + ↑(j + 1)) * (1 - z + ↑j) = ↑((j + 1) ^ 2) * (1 - z ^ 2 / (↑j + 1) ^ 2)
⊢ ↑n ! ^ 2 ≠ 0
state_after: no goals
tactic: exact pow_ne_zero 2 (Nat.cast_ne_zero.mpr <| Nat.factorial_ne_zero n)