-- Mathlib/RingTheory/Valuation/ValuationRing.lean
theorem le_total (a b : ValueGroup A K) : a ≤ b ∨ b ≤ a

Proof state:
case mk.mk.intro.intro.intro.intro.intro.intro.intro.inl.h
A : Type u
inst✝⁵ : CommRing A
K : Type v
inst✝⁴ : Field K
inst✝³ : Algebra A K
inst✝² : IsDomain A
inst✝¹ : ValuationRing A
inst✝ : IsFractionRing A K
a b : ValueGroup A K
xa ya : A
hya : ya ∈ nonZeroDivisors A
xb yb : A
hyb : yb ∈ nonZeroDivisors A
this✝ : (algebraMap A K) ya ≠ 0
this : (algebraMap A K) yb ≠ 0
c : A
h : xa * yb * c = xb * ya
⊢ Quot.mk (⇑(MulAction.orbitRel Aˣ K)) ((algebraMap A K) xb / (algebraMap A K) yb) ≤
    Quot.mk (⇑(MulAction.orbitRel Aˣ K)) ((algebraMap A K) xa / (algebraMap A K) ya)

Tactic:
use c

Result:
case h
A : Type u
inst✝⁵ : CommRing A
K : Type v
inst✝⁴ : Field K
inst✝³ : Algebra A K
inst✝² : IsDomain A
inst✝¹ : ValuationRing A
inst✝ : IsFractionRing A K
a b : ValueGroup A K
xa ya : A
hya : ya ∈ nonZeroDivisors A
xb yb : A
hyb : yb ∈ nonZeroDivisors A
this✝ : (algebraMap A K) ya ≠ 0
this : (algebraMap A K) yb ≠ 0
c : A
h : xa * yb * c = xb * ya
⊢ c • ((algebraMap A K) xa / (algebraMap A K) ya) = (algebraMap A K) xb / (algebraMap A K) yb

Proof state:
case h
A : Type u
inst✝⁵ : CommRing A
K : Type v
inst✝⁴ : Field K
inst✝³ : Algebra A K
inst✝² : IsDomain A
inst✝¹ : ValuationRing A
inst✝ : IsFractionRing A K
a b : ValueGroup A K
xa ya : A
hya : ya ∈ nonZeroDivisors A
xb yb : A
hyb : yb ∈ nonZeroDivisors A
this✝ : (algebraMap A K) ya ≠ 0
this : (algebraMap A K) yb ≠ 0
c : A
h : xb * ya * c = xa * yb
⊢ (algebraMap A K) c * ((algebraMap A K) xb / (algebraMap A K) yb) = (algebraMap A K) xa / (algebraMap A K) ya

Tactic:
field_simp

Result:
case h
A : Type u
inst✝⁵ : CommRing A
K : Type v
inst✝⁴ : Field K
inst✝³ : Algebra A K
inst✝² : IsDomain A
inst✝¹ : ValuationRing A
inst✝ : IsFractionRing A K
a b : ValueGroup A K
xa ya : A
hya : ya ∈ nonZeroDivisors A
xb yb : A
hyb : yb ∈ nonZeroDivisors A
this✝ : (algebraMap A K) ya ≠ 0
this : (algebraMap A K) yb ≠ 0
c : A
h : xb * ya * c = xa * yb
⊢ (algebraMap A K) c * (algebraMap A K) xb * (algebraMap A K) ya = (algebraMap A K) xa * (algebraMap A K) yb

Proof state:
case h
A : Type u
inst✝⁵ : CommRing A
K : Type v
inst✝⁴ : Field K
inst✝³ : Algebra A K
inst✝² : IsDomain A
inst✝¹ : ValuationRing A
inst✝ : IsFractionRing A K
a b : ValueGroup A K
xa ya : A
hya : ya ∈ nonZeroDivisors A
xb yb : A
hyb : yb ∈ nonZeroDivisors A
this✝ : (algebraMap A K) ya ≠ 0
this : (algebraMap A K) yb ≠ 0
c : A
h : xb * ya * c = xa * yb
⊢ (algebraMap A K) c * (algebraMap A K) xb * (algebraMap A K) ya = (algebraMap A K) xa * (algebraMap A K) yb

Tactic:
simp only [← RingHom.map_mul, ← h]

Result:
case h
A : Type u
inst✝⁵ : CommRing A
K : Type v
inst✝⁴ : Field K
inst✝³ : Algebra A K
inst✝² : IsDomain A
inst✝¹ : ValuationRing A
inst✝ : IsFractionRing A K
a b : ValueGroup A K
xa ya : A
hya : ya ∈ nonZeroDivisors A
xb yb : A
hyb : yb ∈ nonZeroDivisors A
this✝ : (algebraMap A K) ya ≠ 0
this : (algebraMap A K) yb ≠ 0
c : A
h : xb * ya * c = xa * yb
⊢ (algebraMap A K) (c * xb * ya) = (algebraMap A K) (xb * ya * c)

Proof state:
case h
A : Type u
inst✝⁵ : CommRing A
K : Type v
inst✝⁴ : Field K
inst✝³ : Algebra A K
inst✝² : IsDomain A
inst✝¹ : ValuationRing A
inst✝ : IsFractionRing A K
a b : ValueGroup A K
xa ya : A
hya : ya ∈ nonZeroDivisors A
xb yb : A
hyb : yb ∈ nonZeroDivisors A
this✝ : (algebraMap A K) ya ≠ 0
this : (algebraMap A K) yb ≠ 0
c : A
h : xa * yb * c = xb * ya
⊢ (algebraMap A K) c * ((algebraMap A K) xa / (algebraMap A K) ya) = (algebraMap A K) xb / (algebraMap A K) yb

Tactic:
field_simp

Result:
case h
A : Type u
inst✝⁵ : CommRing A
K : Type v
inst✝⁴ : Field K
inst✝³ : Algebra A K
inst✝² : IsDomain A
inst✝¹ : ValuationRing A
inst✝ : IsFractionRing A K
a b : ValueGroup A K
xa ya : A
hya : ya ∈ nonZeroDivisors A
xb yb : A
hyb : yb ∈ nonZeroDivisors A
this✝ : (algebraMap A K) ya ≠ 0
this : (algebraMap A K) yb ≠ 0
c : A
h : xa * yb * c = xb * ya
⊢ (algebraMap A K) c * (algebraMap A K) xa * (algebraMap A K) yb = (algebraMap A K) xb * (algebraMap A K) ya

Proof state:
case mk.mk.intro.intro.intro.intro.intro.intro.intro.inl
A : Type u
inst✝⁵ : CommRing A
K : Type v
inst✝⁴ : Field K
inst✝³ : Algebra A K
inst✝² : IsDomain A
inst✝¹ : ValuationRing A
inst✝ : IsFractionRing A K
a b : ValueGroup A K
xa ya : A
hya : ya ∈ nonZeroDivisors A
xb yb : A
hyb : yb ∈ nonZeroDivisors A
this✝ : (algebraMap A K) ya ≠ 0
this : (algebraMap A K) yb ≠ 0
c : A
h : xa * yb * c = xb * ya
⊢ Quot.mk (⇑(MulAction.orbitRel Aˣ K)) ((algebraMap A K) xa / (algebraMap A K) ya) ≤
      Quot.mk (⇑(MulAction.orbitRel Aˣ K)) ((algebraMap A K) xb / (algebraMap A K) yb) ∨
    Quot.mk (⇑(MulAction.orbitRel Aˣ K)) ((algebraMap A K) xb / (algebraMap A K) yb) ≤
      Quot.mk (⇑(MulAction.orbitRel Aˣ K)) ((algebraMap A K) xa / (algebraMap A K) ya)

Tactic:
right

Result:
case mk.mk.intro.intro.intro.intro.intro.intro.intro.inl.h
A : Type u
inst✝⁵ : CommRing A
K : Type v
inst✝⁴ : Field K
inst✝³ : Algebra A K
inst✝² : IsDomain A
inst✝¹ : ValuationRing A
inst✝ : IsFractionRing A K
a b : ValueGroup A K
xa ya : A
hya : ya ∈ nonZeroDivisors A
xb yb : A
hyb : yb ∈ nonZeroDivisors A
this✝ : (algebraMap A K) ya ≠ 0
this : (algebraMap A K) yb ≠ 0
c : A
h : xa * yb * c = xb * ya
⊢ Quot.mk (⇑(MulAction.orbitRel Aˣ K)) ((algebraMap A K) xb / (algebraMap A K) yb) ≤
    Quot.mk (⇑(MulAction.orbitRel Aˣ K)) ((algebraMap A K) xa / (algebraMap A K) ya)

Proof state:
A : Type u
inst✝⁵ : CommRing A
K : Type v
inst✝⁴ : Field K
inst✝³ : Algebra A K
inst✝² : IsDomain A
inst✝¹ : ValuationRing A
inst✝ : IsFractionRing A K
a b : ValueGroup A K
⊢ a ≤ b ∨ b ≤ a

Tactic:
rcases a with ⟨a⟩

Result:
case mk
A : Type u
inst✝⁵ : CommRing A
K : Type v
inst✝⁴ : Field K
inst✝³ : Algebra A K
inst✝² : IsDomain A
inst✝¹ : ValuationRing A
inst✝ : IsFractionRing A K
a✝ b : ValueGroup A K
a : K
⊢ Quot.mk (⇑(MulAction.orbitRel Aˣ K)) a ≤ b ∨ b ≤ Quot.mk (⇑(MulAction.orbitRel Aˣ K)) a

Proof state:
case mk.mk.intro.intro.intro
A : Type u
inst✝⁵ : CommRing A
K : Type v
inst✝⁴ : Field K
inst✝³ : Algebra A K
inst✝² : IsDomain A
inst✝¹ : ValuationRing A
inst✝ : IsFractionRing A K
a b✝ : ValueGroup A K
b : K
xa ya : A
hya : ya ∈ nonZeroDivisors A
⊢ Quot.mk (⇑(MulAction.orbitRel Aˣ K)) ((algebraMap A K) xa / (algebraMap A K) ya) ≤
      Quot.mk (⇑(MulAction.orbitRel Aˣ K)) b ∨
    Quot.mk (⇑(MulAction.orbitRel Aˣ K)) b ≤
      Quot.mk (⇑(MulAction.orbitRel Aˣ K)) ((algebraMap A K) xa / (algebraMap A K) ya)

Tactic:
obtain ⟨xb, yb, hyb, rfl⟩ : ∃ a b : A, _ := IsFractionRing.div_surjective b

Result:
case mk.mk.intro.intro.intro.intro.intro.intro
A : Type u
inst✝⁵ : CommRing A
K : Type v
inst✝⁴ : Field K
inst✝³ : Algebra A K
inst✝² : IsDomain A
inst✝¹ : ValuationRing A
inst✝ : IsFractionRing A K
a b : ValueGroup A K
xa ya : A
hya : ya ∈ nonZeroDivisors A
xb yb : A
hyb : yb ∈ nonZeroDivisors A
⊢ Quot.mk (⇑(MulAction.orbitRel Aˣ K)) ((algebraMap A K) xa / (algebraMap A K) ya) ≤
      Quot.mk (⇑(MulAction.orbitRel Aˣ K)) ((algebraMap A K) xb / (algebraMap A K) yb) ∨
    Quot.mk (⇑(MulAction.orbitRel Aˣ K)) ((algebraMap A K) xb / (algebraMap A K) yb) ≤
      Quot.mk (⇑(MulAction.orbitRel Aˣ K)) ((algebraMap A K) xa / (algebraMap A K) ya)