Theorem: Polynomial.dickson_one_one_mul
File: Mathlib/RingTheory/Polynomial/Dickson.lean

Proof steps:
state_before: R : Type u_1
S : Type u_2
inst✝¹ : CommRing R
inst✝ : CommRing S
k : ℕ
a : R
m n : ℕ
⊢ dickson 1 1 (m * n) = (dickson 1 1 m).comp (dickson 1 1 n)
state_after: R : Type u_1
S : Type u_2
inst✝¹ : CommRing R
inst✝ : CommRing S
k : ℕ
a : R
m n : ℕ
h : 1 = (Int.castRingHom R) 1
⊢ dickson 1 1 (m * n) = (dickson 1 1 m).comp (dickson 1 1 n)
tactic: have h : (1 : R) = Int.castRingHom R 1 := by simp only [eq_intCast, Int.cast_one]
state_before: R : Type u_1
S : Type u_2
inst✝¹ : CommRing R
inst✝ : CommRing S
k : ℕ
a : R
m n : ℕ
h : 1 = (Int.castRingHom R) 1
⊢ dickson 1 1 (m * n) = (dickson 1 1 m).comp (dickson 1 1 n)
state_after: R : Type u_1
S : Type u_2
inst✝¹ : CommRing R
inst✝ : CommRing S
k : ℕ
a : R
m n : ℕ
h : 1 = (Int.castRingHom R) 1
⊢ dickson 1 ((Int.castRingHom R) 1) (m * n) =
    (dickson 1 ((Int.castRingHom R) 1) m).comp (dickson 1 ((Int.castRingHom R) 1) n)
tactic: rw [h]
state_before: R : Type u_1
S : Type u_2
inst✝¹ : CommRing R
inst✝ : CommRing S
k : ℕ
a : R
m n : ℕ
h : 1 = (Int.castRingHom R) 1
⊢ dickson 1 ((Int.castRingHom R) 1) (m * n) =
    (dickson 1 ((Int.castRingHom R) 1) m).comp (dickson 1 ((Int.castRingHom R) 1) n)
state_after: R : Type u_1
S : Type u_2
inst✝¹ : CommRing R
inst✝ : CommRing S
k : ℕ
a : R
m n : ℕ
h : 1 = (Int.castRingHom R) 1
⊢ map (Int.castRingHom R) (dickson 1 1 (m * n)) = map (Int.castRingHom R) ((dickson 1 1 m).comp (dickson 1 1 n))
tactic: simp only [← map_dickson (Int.castRingHom R), ← map_comp]
state_before: R : Type u_1
S : Type u_2
inst✝¹ : CommRing R
inst✝ : CommRing S
k : ℕ
a : R
m n : ℕ
h : 1 = (Int.castRingHom R) 1
⊢ map (Int.castRingHom R) (dickson 1 1 (m * n)) = map (Int.castRingHom R) ((dickson 1 1 m).comp (dickson 1 1 n))
state_after: case e_a
R : Type u_1
S : Type u_2
inst✝¹ : CommRing R
inst✝ : CommRing S
k : ℕ
a : R
m n : ℕ
h : 1 = (Int.castRingHom R) 1
⊢ dickson 1 1 (m * n) = (dickson 1 1 m).comp (dickson 1 1 n)
tactic: congr 1
state_before: case e_a
R : Type u_1
S : Type u_2
inst✝¹ : CommRing R
inst✝ : CommRing S
k : ℕ
a : R
m n : ℕ
h : 1 = (Int.castRingHom R) 1
⊢ dickson 1 1 (m * n) = (dickson 1 1 m).comp (dickson 1 1 n)
state_after: case e_a.a
R : Type u_1
S : Type u_2
inst✝¹ : CommRing R
inst✝ : CommRing S
k : ℕ
a : R
m n : ℕ
h : 1 = (Int.castRingHom R) 1
⊢ map (Int.castRingHom ℚ) (dickson 1 1 (m * n)) = map (Int.castRingHom ℚ) ((dickson 1 1 m).comp (dickson 1 1 n))
tactic: apply map_injective (Int.castRingHom ℚ) Int.cast_injective
state_before: case e_a.a
R : Type u_1
S : Type u_2
inst✝¹ : CommRing R
inst✝ : CommRing S
k : ℕ
a : R
m n : ℕ
h : 1 = (Int.castRingHom R) 1
⊢ map (Int.castRingHom ℚ) (dickson 1 1 (m * n)) = map (Int.castRingHom ℚ) ((dickson 1 1 m).comp (dickson 1 1 n))
state_after: case e_a.a
R : Type u_1
S : Type u_2
inst✝¹ : CommRing R
inst✝ : CommRing S
k : ℕ
a : R
m n : ℕ
h : 1 = (Int.castRingHom R) 1
⊢ ((Chebyshev.T ℚ ↑m + Chebyshev.T ℚ ↑m).comp (Chebyshev.T ℚ ↑n)).comp (C ⅟2 * X) =
    ((Chebyshev.T ℚ ↑m + Chebyshev.T ℚ ↑m).comp (C ⅟2 * X)).comp ((Chebyshev.T ℚ ↑n + Chebyshev.T ℚ ↑n).comp (C ⅟2 * X))
tactic: simp only [map_dickson, map_comp, eq_intCast, Int.cast_one, dickson_one_one_eq_chebyshev_T,
    Nat.cast_mul, Chebyshev.T_mul, two_mul, ← add_comp]
state_before: case e_a.a
R : Type u_1
S : Type u_2
inst✝¹ : CommRing R
inst✝ : CommRing S
k : ℕ
a : R
m n : ℕ
h : 1 = (Int.castRingHom R) 1
⊢ ((Chebyshev.T ℚ ↑m + Chebyshev.T ℚ ↑m).comp (Chebyshev.T ℚ ↑n)).comp (C ⅟2 * X) =
    ((Chebyshev.T ℚ ↑m + Chebyshev.T ℚ ↑m).comp (C ⅟2 * X)).comp ((Chebyshev.T ℚ ↑n + Chebyshev.T ℚ ↑n).comp (C ⅟2 * X))
state_after: case e_a.a
R : Type u_1
S : Type u_2
inst✝¹ : CommRing R
inst✝ : CommRing S
k : ℕ
a : R
m n : ℕ
h : 1 = (Int.castRingHom R) 1
⊢ ((2 * Chebyshev.T ℚ ↑m).comp (Chebyshev.T ℚ ↑n)).comp (C ⅟2 * X) =
    (((2 * Chebyshev.T ℚ ↑m).comp (C ⅟2 * X)).comp (2 * Chebyshev.T ℚ ↑n)).comp (C ⅟2 * X)
tactic: simp only [← two_mul, ← comp_assoc]
state_before: case e_a.a
R : Type u_1
S : Type u_2
inst✝¹ : CommRing R
inst✝ : CommRing S
k : ℕ
a : R
m n : ℕ
h : 1 = (Int.castRingHom R) 1
⊢ ((2 * Chebyshev.T ℚ ↑m).comp (Chebyshev.T ℚ ↑n)).comp (C ⅟2 * X) =
    (((2 * Chebyshev.T ℚ ↑m).comp (C ⅟2 * X)).comp (2 * Chebyshev.T ℚ ↑n)).comp (C ⅟2 * X)
state_after: case e_a.a
R : Type u_1
S : Type u_2
inst✝¹ : CommRing R
inst✝ : CommRing S
k : ℕ
a : R
m n : ℕ
h : 1 = (Int.castRingHom R) 1
⊢ (2 * Chebyshev.T ℚ ↑m).comp (Chebyshev.T ℚ ↑n) = ((2 * Chebyshev.T ℚ ↑m).comp (C ⅟2 * X)).comp (2 * Chebyshev.T ℚ ↑n)
tactic: apply eval₂_congr rfl rfl
state_before: case e_a.a
R : Type u_1
S : Type u_2
inst✝¹ : CommRing R
inst✝ : CommRing S
k : ℕ
a : R
m n : ℕ
h : 1 = (Int.castRingHom R) 1
⊢ (2 * Chebyshev.T ℚ ↑m).comp (Chebyshev.T ℚ ↑n) = ((2 * Chebyshev.T ℚ ↑m).comp (C ⅟2 * X)).comp (2 * Chebyshev.T ℚ ↑n)
state_after: case e_a.a
R : Type u_1
S : Type u_2
inst✝¹ : CommRing R
inst✝ : CommRing S
k : ℕ
a : R
m n : ℕ
h : 1 = (Int.castRingHom R) 1
⊢ (2 * Chebyshev.T ℚ ↑m).comp (Chebyshev.T ℚ ↑n) = (2 * Chebyshev.T ℚ ↑m).comp ((C ⅟2 * X).comp (2 * Chebyshev.T ℚ ↑n))
tactic: rw [comp_assoc]
state_before: case e_a.a
R : Type u_1
S : Type u_2
inst✝¹ : CommRing R
inst✝ : CommRing S
k : ℕ
a : R
m n : ℕ
h : 1 = (Int.castRingHom R) 1
⊢ (2 * Chebyshev.T ℚ ↑m).comp (Chebyshev.T ℚ ↑n) = (2 * Chebyshev.T ℚ ↑m).comp ((C ⅟2 * X).comp (2 * Chebyshev.T ℚ ↑n))
state_after: R : Type u_1
S : Type u_2
inst✝¹ : CommRing R
inst✝ : CommRing S
k : ℕ
a : R
m n : ℕ
h : 1 = (Int.castRingHom R) 1
⊢ Chebyshev.T ℚ ↑n = (C ⅟2 * X).comp (2 * Chebyshev.T ℚ ↑n)
tactic: apply eval₂_congr rfl _ rfl
state_before: R : Type u_1
S : Type u_2
inst✝¹ : CommRing R
inst✝ : CommRing S
k : ℕ
a : R
m n : ℕ
h : 1 = (Int.castRingHom R) 1
⊢ Chebyshev.T ℚ ↑n = (C ⅟2 * X).comp (2 * Chebyshev.T ℚ ↑n)
state_after: no goals
tactic: rw [mul_comp, C_comp, X_comp, ← mul_assoc, C_half_mul_two_eq_one, one_mul]