-- Mathlib/RingTheory/Artinian/Module.lean
theorem surjective_of_injective_endomorphism (f : M →ₗ[R] M) (s : Injective f) : Surjective f

Proof state:
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : M →ₗ[R] M
s : Injective ⇑f
h : ¬Surjective ⇑f
⊢ ∀ (n : ℕ), (fun x => LinearMap.range (f ^ x)) (n + 1) < (fun x => LinearMap.range (f ^ x)) n

Tactic:
intro n

Result:
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : M →ₗ[R] M
s : Injective ⇑f
h : ¬Surjective ⇑f
n : ℕ
⊢ (fun x => LinearMap.range (f ^ x)) (n + 1) < (fun x => LinearMap.range (f ^ x)) n

Proof state:
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : M →ₗ[R] M
s : Injective ⇑f
h : IsArtinian R M
⊢ Surjective ⇑f

Tactic:
contrapose! h

Result:
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : M →ₗ[R] M
s : Injective ⇑f
h : ¬Surjective ⇑f
⊢ ¬IsArtinian R M

Proof state:
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : M →ₗ[R] M
s : Injective ⇑f
h : ¬Surjective ⇑f
⊢ ¬IsArtinian R M

Tactic:
rw [IsArtinian, WellFoundedLT, isWellFounded_iff]

Result:
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : M →ₗ[R] M
s : Injective ⇑f
h : ¬Surjective ⇑f
⊢ ¬WellFounded fun x1 x2 => x1 < x2

Proof state:
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : M →ₗ[R] M
s : Injective ⇑f
h : ¬Surjective ⇑f
n : ℕ
⊢ (fun x => LinearMap.range (f ^ x)) (n + 1) < (fun x => LinearMap.range (f ^ x)) n

Tactic:
simp_rw [pow_succ, LinearMap.mul_eq_comp, LinearMap.range_comp, ← Submodule.map_top (f ^ n)]

Result:
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : M →ₗ[R] M
s : Injective ⇑f
h : ¬Surjective ⇑f
n : ℕ
⊢ Submodule.map (f ^ n) (LinearMap.range f) < Submodule.map (f ^ n) ⊤

Proof state:
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : M →ₗ[R] M
s : Injective ⇑f
h : ¬Surjective ⇑f
n : ℕ
⊢ Submodule.map (f ^ n) (LinearMap.range f) < Submodule.map (f ^ n) ⊤

Tactic:
refine Submodule.map_strictMono_of_injective (LinearMap.iterate_injective s n) (Ne.lt_top ?_)

Result:
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : M →ₗ[R] M
s : Injective ⇑f
h : ¬Surjective ⇑f
n : ℕ
⊢ LinearMap.range f ≠ ⊤

Proof state:
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : M →ₗ[R] M
s : Injective ⇑f
h : ¬Surjective ⇑f
n : ℕ
⊢ LinearMap.range f ≠ ⊤

Tactic:
rwa [Ne, LinearMap.range_eq_top]

Result:
no goals

Proof state:
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : M →ₗ[R] M
s : Injective ⇑f
⊢ Surjective ⇑f

Tactic:
have h := ‹IsArtinian R M›

Result:
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : M →ₗ[R] M
s : Injective ⇑f
h : IsArtinian R M
⊢ Surjective ⇑f