-- Mathlib/RingTheory/Derivation/MapCoeffs.lean
lemma algHom_deriv (f : R →ₐ[A] R') (hf : Function.Injective f) (x : R) (h : IsSeparable A x) :
    f (x′) = (f x)′

Proof state:
case h
A : Type u_1
inst✝¹¹ : CommRing A
inst✝¹⁰ : Differential A
R : Type u_2
inst✝⁹ : CommRing R
inst✝⁸ : Differential R
inst✝⁷ : Algebra A R
inst✝⁶ : DifferentialAlgebra A R
R' : Type u_3
inst✝⁵ : CommRing R'
inst✝⁴ : Differential R'
inst✝³ : Algebra A R'
inst✝² : DifferentialAlgebra A R'
inst✝¹ : IsDomain R'
inst✝ : Nontrivial R
f : R →ₐ[A] R'
hf : Function.Injective ⇑f
x : R
h : IsSeparable A x
p : A[X] := minpoly A x
⊢ (aeval (f x)) (derivative p) * f x′ = (aeval (f x)) (derivative p) * (f x)′

Tactic:
conv => lhs; rw [Polynomial.aeval_algHom]

Result:
case h
A : Type u_1
inst✝¹¹ : CommRing A
inst✝¹⁰ : Differential A
R : Type u_2
inst✝⁹ : CommRing R
inst✝⁸ : Differential R
inst✝⁷ : Algebra A R
inst✝⁶ : DifferentialAlgebra A R
R' : Type u_3
inst✝⁵ : CommRing R'
inst✝⁴ : Differential R'
inst✝³ : Algebra A R'
inst✝² : DifferentialAlgebra A R'
inst✝¹ : IsDomain R'
inst✝ : Nontrivial R
f : R →ₐ[A] R'
hf : Function.Injective ⇑f
x : R
h : IsSeparable A x
p : A[X] := minpoly A x
⊢ (f.comp (aeval x)) (derivative p) * f x′ = (aeval (f x)) (derivative p) * (f x)′

Proof state:
case h
A : Type u_1
inst✝¹¹ : CommRing A
inst✝¹⁰ : Differential A
R : Type u_2
inst✝⁹ : CommRing R
inst✝⁸ : Differential R
inst✝⁷ : Algebra A R
inst✝⁶ : DifferentialAlgebra A R
R' : Type u_3
inst✝⁵ : CommRing R'
inst✝⁴ : Differential R'
inst✝³ : Algebra A R'
inst✝² : DifferentialAlgebra A R'
inst✝¹ : IsDomain R'
inst✝ : Nontrivial R
f : R →ₐ[A] R'
hf : Function.Injective ⇑f
x : R
h : IsSeparable A x
p : A[X] := minpoly A x
⊢ f ((aeval x) (derivative p) * x′) = (aeval (f x)) (derivative p) * (f x)′

Tactic:
apply add_left_cancel (a := aeval (f x) (mapCoeffs p))

Result:
case h
A : Type u_1
inst✝¹¹ : CommRing A
inst✝¹⁰ : Differential A
R : Type u_2
inst✝⁹ : CommRing R
inst✝⁸ : Differential R
inst✝⁷ : Algebra A R
inst✝⁶ : DifferentialAlgebra A R
R' : Type u_3
inst✝⁵ : CommRing R'
inst✝⁴ : Differential R'
inst✝³ : Algebra A R'
inst✝² : DifferentialAlgebra A R'
inst✝¹ : IsDomain R'
inst✝ : Nontrivial R
f : R →ₐ[A] R'
hf : Function.Injective ⇑f
x : R
h : IsSeparable A x
p : A[X] := minpoly A x
⊢ (aeval (f x)) (mapCoeffs p) + f ((aeval x) (derivative p) * x′) =
    (aeval (f x)) (mapCoeffs p) + (aeval (f x)) (derivative p) * (f x)′

Proof state:
case h
A : Type u_1
inst✝¹¹ : CommRing A
inst✝¹⁰ : Differential A
R : Type u_2
inst✝⁹ : CommRing R
inst✝⁸ : Differential R
inst✝⁷ : Algebra A R
inst✝⁶ : DifferentialAlgebra A R
R' : Type u_3
inst✝⁵ : CommRing R'
inst✝⁴ : Differential R'
inst✝³ : Algebra A R'
inst✝² : DifferentialAlgebra A R'
inst✝¹ : IsDomain R'
inst✝ : Nontrivial R
f : R →ₐ[A] R'
hf : Function.Injective ⇑f
x : R
h : IsSeparable A x
p : A[X] := minpoly A x
⊢ (aeval (f x)) (mapCoeffs p) + f ((aeval x) (derivative p) * x′) =
    (aeval (f x)) (mapCoeffs p) + (aeval (f x)) (derivative p) * (f x)′

Tactic:
rw [← deriv_aeval_eq]

Result:
case h
A : Type u_1
inst✝¹¹ : CommRing A
inst✝¹⁰ : Differential A
R : Type u_2
inst✝⁹ : CommRing R
inst✝⁸ : Differential R
inst✝⁷ : Algebra A R
inst✝⁶ : DifferentialAlgebra A R
R' : Type u_3
inst✝⁵ : CommRing R'
inst✝⁴ : Differential R'
inst✝³ : Algebra A R'
inst✝² : DifferentialAlgebra A R'
inst✝¹ : IsDomain R'
inst✝ : Nontrivial R
f : R →ₐ[A] R'
hf : Function.Injective ⇑f
x : R
h : IsSeparable A x
p : A[X] := minpoly A x
⊢ (aeval (f x)) (mapCoeffs p) + f ((aeval x) (derivative p) * x′) = ((aeval (f x)) p)′

Proof state:
case ha
A : Type u_1
inst✝¹¹ : CommRing A
inst✝¹⁰ : Differential A
R : Type u_2
inst✝⁹ : CommRing R
inst✝⁸ : Differential R
inst✝⁷ : Algebra A R
inst✝⁶ : DifferentialAlgebra A R
R' : Type u_3
inst✝⁵ : CommRing R'
inst✝⁴ : Differential R'
inst✝³ : Algebra A R'
inst✝² : DifferentialAlgebra A R'
inst✝¹ : IsDomain R'
inst✝ : Nontrivial R
f : R →ₐ[A] R'
hf : Function.Injective ⇑f
x : R
h : IsSeparable A x
p : A[X] := minpoly A x
⊢ ¬(aeval x) (derivative p) = 0

Tactic:
apply Separable.aeval_derivative_ne_zero h (minpoly.aeval A x)

Result:
no goals

Proof state:
case h
A : Type u_1
inst✝¹¹ : CommRing A
inst✝¹⁰ : Differential A
R : Type u_2
inst✝⁹ : CommRing R
inst✝⁸ : Differential R
inst✝⁷ : Algebra A R
inst✝⁶ : DifferentialAlgebra A R
R' : Type u_3
inst✝⁵ : CommRing R'
inst✝⁴ : Differential R'
inst✝³ : Algebra A R'
inst✝² : DifferentialAlgebra A R'
inst✝¹ : IsDomain R'
inst✝ : Nontrivial R
f : R →ₐ[A] R'
hf : Function.Injective ⇑f
x : R
h : IsSeparable A x
p : A[X] := minpoly A x
⊢ (aeval (f x)) (mapCoeffs p) + f ((aeval x) (derivative p) * x′) = ((aeval (f x)) p)′

Tactic:
simp only [aeval_algHom, AlgHom.coe_comp, Function.comp_apply, ← map_add, ← deriv_aeval_eq,
  minpoly.aeval, map_zero, p]

Result:
no goals

Proof state:
case h
A : Type u_1
inst✝¹¹ : CommRing A
inst✝¹⁰ : Differential A
R : Type u_2
inst✝⁹ : CommRing R
inst✝⁸ : Differential R
inst✝⁷ : Algebra A R
inst✝⁶ : DifferentialAlgebra A R
R' : Type u_3
inst✝⁵ : CommRing R'
inst✝⁴ : Differential R'
inst✝³ : Algebra A R'
inst✝² : DifferentialAlgebra A R'
inst✝¹ : IsDomain R'
inst✝ : Nontrivial R
f : R →ₐ[A] R'
hf : Function.Injective ⇑f
x : R
h : IsSeparable A x
p : A[X] := minpoly A x
⊢ (f.comp (aeval x)) (derivative p) * f x′ = (aeval (f x)) (derivative p) * (f x)′

Tactic:
simp [← map_mul]

Result:
case h
A : Type u_1
inst✝¹¹ : CommRing A
inst✝¹⁰ : Differential A
R : Type u_2
inst✝⁹ : CommRing R
inst✝⁸ : Differential R
inst✝⁷ : Algebra A R
inst✝⁶ : DifferentialAlgebra A R
R' : Type u_3
inst✝⁵ : CommRing R'
inst✝⁴ : Differential R'
inst✝³ : Algebra A R'
inst✝² : DifferentialAlgebra A R'
inst✝¹ : IsDomain R'
inst✝ : Nontrivial R
f : R →ₐ[A] R'
hf : Function.Injective ⇑f
x : R
h : IsSeparable A x
p : A[X] := minpoly A x
⊢ f ((aeval x) (derivative p) * x′) = (aeval (f x)) (derivative p) * (f x)′

Proof state:
A : Type u_1
inst✝¹¹ : CommRing A
inst✝¹⁰ : Differential A
R : Type u_2
inst✝⁹ : CommRing R
inst✝⁸ : Differential R
inst✝⁷ : Algebra A R
inst✝⁶ : DifferentialAlgebra A R
R' : Type u_3
inst✝⁵ : CommRing R'
inst✝⁴ : Differential R'
inst✝³ : Algebra A R'
inst✝² : DifferentialAlgebra A R'
inst✝¹ : IsDomain R'
inst✝ : Nontrivial R
f : R →ₐ[A] R'
hf : Function.Injective ⇑f
x : R
h : IsSeparable A x
p : A[X] := minpoly A x
⊢ f x′ = (f x)′

Tactic:
apply mul_left_cancel₀ (a := aeval (f x) (derivative p))

Result:
case ha
A : Type u_1
inst✝¹¹ : CommRing A
inst✝¹⁰ : Differential A
R : Type u_2
inst✝⁹ : CommRing R
inst✝⁸ : Differential R
inst✝⁷ : Algebra A R
inst✝⁶ : DifferentialAlgebra A R
R' : Type u_3
inst✝⁵ : CommRing R'
inst✝⁴ : Differential R'
inst✝³ : Algebra A R'
inst✝² : DifferentialAlgebra A R'
inst✝¹ : IsDomain R'
inst✝ : Nontrivial R
f : R →ₐ[A] R'
hf : Function.Injective ⇑f
x : R
h : IsSeparable A x
p : A[X] := minpoly A x
⊢ (aeval (f x)) (derivative p) ≠ 0

case h
A : Type u_1
inst✝¹¹ : CommRing A
inst✝¹⁰ : Differential A
R : Type u_2
inst✝⁹ : CommRing R
inst✝⁸ : Differential R
inst✝⁷ : Algebra A R
inst✝⁶ : DifferentialAlgebra A R
R' : Type u_3
inst✝⁵ : CommRing R'
inst✝⁴ : Differential R'
inst✝³ : Algebra A R'
inst✝² : DifferentialAlgebra A R'
inst✝¹ : IsDomain R'
inst✝ : Nontrivial R
f : R →ₐ[A] R'
hf : Function.Injective ⇑f
x : R
h : IsSeparable A x
p : A[X] := minpoly A x
⊢ (aeval (f x)) (derivative p) * f x′ = (aeval (f x)) (derivative p) * (f x)′