Theorem: minpolyDiv_monic
File: Mathlib/FieldTheory/Minpoly/MinpolyDiv.lean

tactic: nontriviality S
state_before: R : Type u_2
K : Type ?u.14676
L : Type ?u.14679
S : Type u_1
inst✝⁵ : CommRing R
inst✝⁴ : Field K
inst✝³ : Field L
inst✝² : CommRing S
inst✝¹ : Algebra R S
inst✝ : Algebra K L
x : S
hx : IsIntegral R x
⊢ (minpolyDiv R x).Monic
state_after: R : Type u_2
K : Type ?u.14676
L : Type ?u.14679
S : Type u_1
inst✝⁵ : CommRing R
inst✝⁴ : Field K
inst✝³ : Field L
inst✝² : CommRing S
inst✝¹ : Algebra R S
inst✝ : Algebra K L
x : S
hx : IsIntegral R x
a✝ : Nontrivial S
⊢ (minpolyDiv R x).Monic

tactic: have := congr_arg leadingCoeff (minpolyDiv_spec R x)
state_before: R : Type u_2
K : Type ?u.14676
L : Type ?u.14679
S : Type u_1
inst✝⁵ : CommRing R
inst✝⁴ : Field K
inst✝³ : Field L
inst✝² : CommRing S
inst✝¹ : Algebra R S
inst✝ : Algebra K L
x : S
hx : IsIntegral R x
a✝ : Nontrivial S
⊢ (minpolyDiv R x).Monic
state_after: R : Type u_2
K : Type ?u.14676
L : Type ?u.14679
S : Type u_1
inst✝⁵ : CommRing R
inst✝⁴ : Field K
inst✝³ : Field L
inst✝² : CommRing S
inst✝¹ : Algebra R S
inst✝ : Algebra K L
x : S
hx : IsIntegral R x
a✝ : Nontrivial S
this : (minpolyDiv R x * (X - C x)).leadingCoeff = (map (algebraMap R S) (minpoly R x)).leadingCoeff
⊢ (minpolyDiv R x).Monic

tactic: rw [leadingCoeff_mul', ((minpoly.monic hx).map (algebraMap R S)).leadingCoeff] at this
state_before: R : Type u_2
K : Type ?u.14676
L : Type ?u.14679
S : Type u_1
inst✝⁵ : CommRing R
inst✝⁴ : Field K
inst✝³ : Field L
inst✝² : CommRing S
inst✝¹ : Algebra R S
inst✝ : Algebra K L
x : S
hx : IsIntegral R x
a✝ : Nontrivial S
this : (minpolyDiv R x * (X - C x)).leadingCoeff = (map (algebraMap R S) (minpoly R x)).leadingCoeff
⊢ (minpolyDiv R x).Monic
state_after: R : Type u_2
K : Type ?u.14676
L : Type ?u.14679
S : Type u_1
inst✝⁵ : CommRing R
inst✝⁴ : Field K
inst✝³ : Field L
inst✝² : CommRing S
inst✝¹ : Algebra R S
inst✝ : Algebra K L
x : S
hx : IsIntegral R x
a✝ : Nontrivial S
this : (minpolyDiv R x).leadingCoeff * (X - C x).leadingCoeff = 1
⊢ (minpolyDiv R x).Monic

R : Type u_2
K : Type ?u.14676
L : Type ?u.14679
S : Type u_1
inst✝⁵ : CommRing R
inst✝⁴ : Field K
inst✝³ : Field L
inst✝² : CommRing S
inst✝¹ : Algebra R S
inst✝ : Algebra K L
x : S
hx : IsIntegral R x
a✝ : Nontrivial S
this : (minpolyDiv R x * (X - C x)).leadingCoeff = (map (algebraMap R S) (minpoly R x)).leadingCoeff
⊢ (minpolyDiv R x).leadingCoeff * (X - C x).leadingCoeff ≠ 0

tactic: simpa using this
state_before: R : Type u_2
K : Type ?u.14676
L : Type ?u.14679
S : Type u_1
inst✝⁵ : CommRing R
inst✝⁴ : Field K
inst✝³ : Field L
inst✝² : CommRing S
inst✝¹ : Algebra R S
inst✝ : Algebra K L
x : S
hx : IsIntegral R x
a✝ : Nontrivial S
this : (minpolyDiv R x).leadingCoeff * (X - C x).leadingCoeff = 1
⊢ (minpolyDiv R x).Monic
state_after: no goals

tactic: simpa using minpolyDiv_ne_zero hx
state_before: R : Type u_2
K : Type ?u.14676
L : Type ?u.14679
S : Type u_1
inst✝⁵ : CommRing R
inst✝⁴ : Field K
inst✝³ : Field L
inst✝² : CommRing S
inst✝¹ : Algebra R S
inst✝ : Algebra K L
x : S
hx : IsIntegral R x
a✝ : Nontrivial S
this : (minpolyDiv R x * (X - C x)).leadingCoeff = (map (algebraMap R S) (minpoly R x)).leadingCoeff
⊢ (minpolyDiv R x).leadingCoeff * (X - C x).leadingCoeff ≠ 0
state_after: no goals