Theorem: Polynomial.isCoprime_scaleRoots
File: Mathlib/RingTheory/Polynomial/ScaleRoots.lean

Proof steps:
state_before: R : Type u_1
S : Type u_2
A : Type u_3
K : Type u_4
inst✝³ : Semiring S
inst✝² : CommSemiring R
inst✝¹ : Semiring A
inst✝ : Field K
p q : R[X]
r : R
hr : IsUnit r
h : IsCoprime p q
⊢ IsCoprime (p.scaleRoots r) (q.scaleRoots r)
state_after: case intro.intro
R : Type u_1
S : Type u_2
A : Type u_3
K : Type u_4
inst✝³ : Semiring S
inst✝² : CommSemiring R
inst✝¹ : Semiring A
inst✝ : Field K
p q : R[X]
r : R
hr : IsUnit r
a b : R[X]
e : a * p + b * q = 1
⊢ IsCoprime (p.scaleRoots r) (q.scaleRoots r)
tactic: obtain ⟨a, b, e⟩ := h
state_before: case intro.intro
R : Type u_1
S : Type u_2
A : Type u_3
K : Type u_4
inst✝³ : Semiring S
inst✝² : CommSemiring R
inst✝¹ : Semiring A
inst✝ : Field K
p q : R[X]
r : R
hr : IsUnit r
a b : R[X]
e : a * p + b * q = 1
⊢ IsCoprime (p.scaleRoots r) (q.scaleRoots r)
state_after: case intro.intro
R : Type u_1
S : Type u_2
A : Type u_3
K : Type u_4
inst✝³ : Semiring S
inst✝² : CommSemiring R
inst✝¹ : Semiring A
inst✝ : Field K
p q : R[X]
r : R
hr : IsUnit r
a b : R[X]
e : a * p + b * q = 1
s : R := ↑hr.unit⁻¹
⊢ IsCoprime (p.scaleRoots r) (q.scaleRoots r)
tactic: let s : R := ↑hr.unit⁻¹
state_before: case intro.intro
R : Type u_1
S : Type u_2
A : Type u_3
K : Type u_4
inst✝³ : Semiring S
inst✝² : CommSemiring R
inst✝¹ : Semiring A
inst✝ : Field K
p q : R[X]
r : R
hr : IsUnit r
a b : R[X]
e : a * p + b * q = 1
s : R := ↑hr.unit⁻¹
⊢ IsCoprime (p.scaleRoots r) (q.scaleRoots r)
state_after: case intro.intro
R : Type u_1
S : Type u_2
A : Type u_3
K : Type u_4
inst✝³ : Semiring S
inst✝² : CommSemiring R
inst✝¹ : Semiring A
inst✝ : Field K
p q : R[X]
r : R
hr : IsUnit r
a b : R[X]
e : a * p + b * q = 1
s : R := ↑hr.unit⁻¹
this : (a * p).natDegree = (b * q).natDegree
⊢ IsCoprime (p.scaleRoots r) (q.scaleRoots r)
tactic: have : natDegree (a * p) = natDegree (b * q) := by
    apply natDegree_eq_of_natDegree_add_eq_zero
    rw [e, natDegree_one]
state_before: case intro.intro
R : Type u_1
S : Type u_2
A : Type u_3
K : Type u_4
inst✝³ : Semiring S
inst✝² : CommSemiring R
inst✝¹ : Semiring A
inst✝ : Field K
p q : R[X]
r : R
hr : IsUnit r
a b : R[X]
e : a * p + b * q = 1
s : R := ↑hr.unit⁻¹
this : (a * p).natDegree = (b * q).natDegree
⊢ IsCoprime (p.scaleRoots r) (q.scaleRoots r)
state_after: case h
R : Type u_1
S : Type u_2
A : Type u_3
K : Type u_4
inst✝³ : Semiring S
inst✝² : CommSemiring R
inst✝¹ : Semiring A
inst✝ : Field K
p q : R[X]
r : R
hr : IsUnit r
a b : R[X]
e : a * p + b * q = 1
s : R := ↑hr.unit⁻¹
this : (a * p).natDegree = (b * q).natDegree
⊢ ∃ b,
    s ^ (a * p).natDegree • s ^ (a.natDegree + p.natDegree - (a * p).natDegree) • a.scaleRoots r * p.scaleRoots r +
        b * q.scaleRoots r =
      1
tactic: use s ^ natDegree (a * p) • s ^ (natDegree a + natDegree p - natDegree (a * p)) • a.scaleRoots r
state_before: case h
R : Type u_1
S : Type u_2
A : Type u_3
K : Type u_4
inst✝³ : Semiring S
inst✝² : CommSemiring R
inst✝¹ : Semiring A
inst✝ : Field K
p q : R[X]
r : R
hr : IsUnit r
a b : R[X]
e : a * p + b * q = 1
s : R := ↑hr.unit⁻¹
this : (a * p).natDegree = (b * q).natDegree
⊢ ∃ b,
    s ^ (a * p).natDegree • s ^ (a.natDegree + p.natDegree - (a * p).natDegree) • a.scaleRoots r * p.scaleRoots r +
        b * q.scaleRoots r =
      1
state_after: case h
R : Type u_1
S : Type u_2
A : Type u_3
K : Type u_4
inst✝³ : Semiring S
inst✝² : CommSemiring R
inst✝¹ : Semiring A
inst✝ : Field K
p q : R[X]
r : R
hr : IsUnit r
a b : R[X]
e : a * p + b * q = 1
s : R := ↑hr.unit⁻¹
this : (a * p).natDegree = (b * q).natDegree
⊢ s ^ (a * p).natDegree • s ^ (a.natDegree + p.natDegree - (a * p).natDegree) • a.scaleRoots r * p.scaleRoots r +
      s ^ (a * p).natDegree • s ^ (b.natDegree + q.natDegree - (b * q).natDegree) • b.scaleRoots r * q.scaleRoots r =
    1
tactic: use s ^ natDegree (a * p) • s ^ (natDegree b + natDegree q - natDegree (b * q)) • b.scaleRoots r
state_before: case h
R : Type u_1
S : Type u_2
A : Type u_3
K : Type u_4
inst✝³ : Semiring S
inst✝² : CommSemiring R
inst✝¹ : Semiring A
inst✝ : Field K
p q : R[X]
r : R
hr : IsUnit r
a b : R[X]
e : a * p + b * q = 1
s : R := ↑hr.unit⁻¹
this : (a * p).natDegree = (b * q).natDegree
⊢ s ^ (a * p).natDegree • s ^ (a.natDegree + p.natDegree - (a * p).natDegree) • a.scaleRoots r * p.scaleRoots r +
      s ^ (a * p).natDegree • s ^ (b.natDegree + q.natDegree - (b * q).natDegree) • b.scaleRoots r * q.scaleRoots r =
    1
state_after: no goals
tactic: simp only [s, smul_mul_assoc, ← mul_scaleRoots, smul_smul, Units.smul_def, mul_assoc,
    ← mul_pow, IsUnit.val_inv_mul, one_pow, mul_one, ← smul_add, one_smul, e, natDegree_one,
    one_scaleRoots, ← add_scaleRoots_of_natDegree_eq _ _ _ this, tsub_zero]