-- Mathlib/RingTheory/Polynomial/Bernstein.lean
theorem sum_smul (n : ℕ) :
    (∑ ν ∈ Finset.range (n + 1), ν • bernsteinPolynomial R n ν) = n • X

Proof state:
R : Type u_1
inst✝ : CommRing R
n : ℕ
x : MvPolynomial Bool R := MvPolynomial.X true
y : MvPolynomial Bool R := MvPolynomial.X false
pderiv_true_x : (pderiv true) x = 1
⊢ (pderiv true) y = 0

Tactic:
rw [pderiv_X]

Result:
R : Type u_1
inst✝ : CommRing R
n : ℕ
x : MvPolynomial Bool R := MvPolynomial.X true
y : MvPolynomial Bool R := MvPolynomial.X false
pderiv_true_x : (pderiv true) x = 1
⊢ Pi.single true 1 false = 0

Proof state:
R : Type u_1
inst✝ : CommRing R
n : ℕ
x : MvPolynomial Bool R := MvPolynomial.X true
y : MvPolynomial Bool R := MvPolynomial.X false
pderiv_true_x : (pderiv true) x = 1
pderiv_true_y : (pderiv true) y = 0
e : Bool → R[X] := fun i => bif i then X else 1 - X
⊢ ∑ ν ∈ Finset.range (n + 1), ν • bernsteinPolynomial R n ν = n • X

Tactic:
trans MvPolynomial.aeval e (pderiv true ((x + y) ^ n)) * X

Result:
R : Type u_1
inst✝ : CommRing R
n : ℕ
x : MvPolynomial Bool R := MvPolynomial.X true
y : MvPolynomial Bool R := MvPolynomial.X false
pderiv_true_x : (pderiv true) x = 1
pderiv_true_y : (pderiv true) y = 0
e : Bool → R[X] := fun i => bif i then X else 1 - X
⊢ ∑ ν ∈ Finset.range (n + 1), ν • bernsteinPolynomial R n ν = (MvPolynomial.aeval e) ((pderiv true) ((x + y) ^ n)) * X

R : Type u_1
inst✝ : CommRing R
n : ℕ
x : MvPolynomial Bool R := MvPolynomial.X true
y : MvPolynomial Bool R := MvPolynomial.X false
pderiv_true_x : (pderiv true) x = 1
pderiv_true_y : (pderiv true) y = 0
e : Bool → R[X] := fun i => bif i then X else 1 - X
⊢ (MvPolynomial.aeval e) ((pderiv true) ((x + y) ^ n)) * X = n • X

Proof state:
R : Type u_1
inst✝ : CommRing R
n : ℕ
x : MvPolynomial Bool R := MvPolynomial.X true
y : MvPolynomial Bool R := MvPolynomial.X false
pderiv_true_x : (pderiv true) x = 1
pderiv_true_y : (pderiv true) y = 0
e : Bool → R[X] := fun i => bif i then X else 1 - X
w : ∀ (k : ℕ), k • bernsteinPolynomial R n k = ↑k * X ^ (k - 1) * (1 - X) ^ (n - k) * ↑(n.choose k) * X
⊢ ∑ ν ∈ Finset.range (n + 1), ν • bernsteinPolynomial R n ν = (MvPolynomial.aeval e) ((pderiv true) ((x + y) ^ n)) * X

Tactic:
rw [add_pow, map_sum (pderiv true), map_sum (MvPolynomial.aeval e), Finset.sum_mul]

Result:
R : Type u_1
inst✝ : CommRing R
n : ℕ
x : MvPolynomial Bool R := MvPolynomial.X true
y : MvPolynomial Bool R := MvPolynomial.X false
pderiv_true_x : (pderiv true) x = 1
pderiv_true_y : (pderiv true) y = 0
e : Bool → R[X] := fun i => bif i then X else 1 - X
w : ∀ (k : ℕ), k • bernsteinPolynomial R n k = ↑k * X ^ (k - 1) * (1 - X) ^ (n - k) * ↑(n.choose k) * X
⊢ ∑ ν ∈ Finset.range (n + 1), ν • bernsteinPolynomial R n ν =
    ∑ i ∈ Finset.range (n + 1), (MvPolynomial.aeval e) ((pderiv true) (x ^ i * y ^ (n - i) * ↑(n.choose i))) * X

Proof state:
R : Type u_1
inst✝ : CommRing R
n : ℕ
x : MvPolynomial Bool R := MvPolynomial.X true
y : MvPolynomial Bool R := MvPolynomial.X false
pderiv_true_x : (pderiv true) x = 1
pderiv_true_y : (pderiv true) y = 0
e : Bool → R[X] := fun i => bif i then X else 1 - X
w : ∀ (k : ℕ), k • bernsteinPolynomial R n k = ↑k * X ^ (k - 1) * (1 - X) ^ (n - k) * ↑(n.choose k) * X
⊢ ∑ ν ∈ Finset.range (n + 1), ν • bernsteinPolynomial R n ν =
    ∑ i ∈ Finset.range (n + 1), (MvPolynomial.aeval e) ((pderiv true) (x ^ i * y ^ (n - i) * ↑(n.choose i))) * X

Tactic:
refine Finset.sum_congr rfl fun k _ => (w k).trans ?_

Result:
R : Type u_1
inst✝ : CommRing R
n : ℕ
x : MvPolynomial Bool R := MvPolynomial.X true
y : MvPolynomial Bool R := MvPolynomial.X false
pderiv_true_x : (pderiv true) x = 1
pderiv_true_y : (pderiv true) y = 0
e : Bool → R[X] := fun i => bif i then X else 1 - X
w : ∀ (k : ℕ), k • bernsteinPolynomial R n k = ↑k * X ^ (k - 1) * (1 - X) ^ (n - k) * ↑(n.choose k) * X
k : ℕ
x✝ : k ∈ Finset.range (n + 1)
⊢ ↑k * X ^ (k - 1) * (1 - X) ^ (n - k) * ↑(n.choose k) * X =
    (MvPolynomial.aeval e) ((pderiv true) (x ^ k * y ^ (n - k) * ↑(n.choose k))) * X

Proof state:
R : Type u_1
inst✝ : CommRing R
n : ℕ
x : MvPolynomial Bool R := MvPolynomial.X true
y : MvPolynomial Bool R := MvPolynomial.X false
pderiv_true_x : (pderiv true) x = 1
pderiv_true_y : (pderiv true) y = 0
⊢ ∑ ν ∈ Finset.range (n + 1), ν • bernsteinPolynomial R n ν = n • X

Tactic:
let e : Bool → R[X] := fun i => cond i X (1 - X)

Result:
R : Type u_1
inst✝ : CommRing R
n : ℕ
x : MvPolynomial Bool R := MvPolynomial.X true
y : MvPolynomial Bool R := MvPolynomial.X false
pderiv_true_x : (pderiv true) x = 1
pderiv_true_y : (pderiv true) y = 0
e : Bool → R[X] := fun i => bif i then X else 1 - X
⊢ ∑ ν ∈ Finset.range (n + 1), ν • bernsteinPolynomial R n ν = n • X

Proof state:
case succ
R : Type u_1
inst✝ : CommRing R
n : ℕ
x : MvPolynomial Bool R := MvPolynomial.X true
y : MvPolynomial Bool R := MvPolynomial.X false
pderiv_true_x : (pderiv true) x = 1
pderiv_true_y : (pderiv true) y = 0
e : Bool → R[X] := fun i => bif i then X else 1 - X
k : ℕ
⊢ (↑k + 1) * (↑(n.choose (k + 1)) * (X ^ k * X) * (1 - X) ^ (n - (k + 1))) =
    (↑k + 1) * X ^ k * (1 - X) ^ (n - (k + 1)) * ↑(n.choose (k + 1)) * X

Tactic:
ring

Result:
no goals

Proof state:
R : Type u_1
inst✝ : CommRing R
n : ℕ
x : MvPolynomial Bool R := MvPolynomial.X true
y : MvPolynomial Bool R := MvPolynomial.X false
pderiv_true_x : (pderiv true) x = 1
pderiv_true_y : (pderiv true) y = 0
e : Bool → R[X] := fun i => bif i then X else 1 - X
⊢ (MvPolynomial.aeval e) ((pderiv true) ((x + y) ^ n)) * X = n • X

Tactic:
rw [(pderiv true).leibniz_pow, (pderiv true).map_add, pderiv_true_x, pderiv_true_y]

Result:
R : Type u_1
inst✝ : CommRing R
n : ℕ
x : MvPolynomial Bool R := MvPolynomial.X true
y : MvPolynomial Bool R := MvPolynomial.X false
pderiv_true_x : (pderiv true) x = 1
pderiv_true_y : (pderiv true) y = 0
e : Bool → R[X] := fun i => bif i then X else 1 - X
⊢ (MvPolynomial.aeval e) (n • (x + y) ^ (n - 1) • (1 + 0)) * X = n • X

Proof state:
R : Type u_1
inst✝ : CommRing R
n : ℕ
x : MvPolynomial Bool R := MvPolynomial.X true
y : MvPolynomial Bool R := MvPolynomial.X false
⊢ Pi.single true 1 true = 1

Tactic:
rfl

Result:
no goals

Proof state:
R : Type u_1
inst✝ : CommRing R
n : ℕ
x : MvPolynomial Bool R := MvPolynomial.X true
y : MvPolynomial Bool R := MvPolynomial.X false
pderiv_true_x : (pderiv true) x = 1
pderiv_true_y : (pderiv true) y = 0
e : Bool → R[X] := fun i => bif i then X else 1 - X
⊢ ∀ (k : ℕ), k • bernsteinPolynomial R n k = ↑k * X ^ (k - 1) * (1 - X) ^ (n - k) * ↑(n.choose k) * X

Tactic:
rintro (_ | k)

Result:
case zero
R : Type u_1
inst✝ : CommRing R
n : ℕ
x : MvPolynomial Bool R := MvPolynomial.X true
y : MvPolynomial Bool R := MvPolynomial.X false
pderiv_true_x : (pderiv true) x = 1
pderiv_true_y : (pderiv true) y = 0
e : Bool → R[X] := fun i => bif i then X else 1 - X
⊢ 0 • bernsteinPolynomial R n 0 = ↑0 * X ^ (0 - 1) * (1 - X) ^ (n - 0) * ↑(n.choose 0) * X

case succ
R : Type u_1
inst✝ : CommRing R
n : ℕ
x : MvPolynomial Bool R := MvPolynomial.X true
y : MvPolynomial Bool R := MvPolynomial.X false
pderiv_true_x : (pderiv true) x = 1
pderiv_true_y : (pderiv true) y = 0
e : Bool → R[X] := fun i => bif i then X else 1 - X
k : ℕ
⊢ (k + 1) • bernsteinPolynomial R n (k + 1) =
    ↑(k + 1) * X ^ (k + 1 - 1) * (1 - X) ^ (n - (k + 1)) * ↑(n.choose (k + 1)) * X

Proof state:
R : Type u_1
inst✝ : CommRing R
n : ℕ
x : MvPolynomial Bool R := MvPolynomial.X true
y : MvPolynomial Bool R := MvPolynomial.X false
pderiv_true_x : (pderiv true) x = 1
⊢ Pi.single true 1 false = 0

Tactic:
rfl

Result:
no goals