Theorem: Subadditive.eventually_div_lt_of_div_lt
File: Mathlib/Analysis/Subadditive.lean

Proof steps:
state_before: u : ℕ → ℝ
h : Subadditive u
L : ℝ
n : ℕ
hn : n ≠ 0
hL : u n / ↑n < L
⊢ ∀ᶠ (p : ℕ) in atTop, u p / ↑p < L
state_after: u : ℕ → ℝ
h : Subadditive u
L : ℝ
n : ℕ
hn : n ≠ 0
hL : u n / ↑n < L
r : ℕ
x✝ : r < n
⊢ ∀ᶠ (a : ℕ) in atTop, u (n * a + r) / ↑(n * a + r) < L
tactic: refine .atTop_of_arithmetic hn fun r _ => ?_
state_before: u : ℕ → ℝ
h : Subadditive u
L : ℝ
n : ℕ
hn : n ≠ 0
hL : u n / ↑n < L
r : ℕ
x✝ : r < n
⊢ ∀ᶠ (a : ℕ) in atTop, u (n * a + r) / ↑(n * a + r) < L
state_after: u : ℕ → ℝ
h : Subadditive u
L : ℝ
n : ℕ
hn : n ≠ 0
hL : u n / ↑n < L
r : ℕ
x✝ : r < n
A : Tendsto (fun x => (u n + u r / x) / (↑n + ↑r / x)) atTop (𝓝 ((u n + 0) / (↑n + 0)))
⊢ ∀ᶠ (a : ℕ) in atTop, u (n * a + r) / ↑(n * a + r) < L
tactic: have A : Tendsto (fun x : ℝ => (u n + u r / x) / (n + r / x)) atTop (𝓝 ((u n + 0) / (n + 0))) :=
    (tendsto_const_nhds.add <| tendsto_const_nhds.div_atTop tendsto_id).div
      (tendsto_const_nhds.add <| tendsto_const_nhds.div_atTop tendsto_id) <| by simpa
state_before: u : ℕ → ℝ
h : Subadditive u
L : ℝ
n : ℕ
hn : n ≠ 0
hL : u n / ↑n < L
r : ℕ
x✝ : r < n
A : Tendsto (fun x => (u n + u r / x) / (↑n + ↑r / x)) atTop (𝓝 ((u n + 0) / (↑n + 0)))
B : Tendsto (fun x => (x * u n + u r) / (x * ↑n + ↑r)) atTop (𝓝 (u n / ↑n))
⊢ ∀ᶠ (a : ℕ) in atTop, u (n * a + r) / ↑(n * a + r) < L
state_after: u : ℕ → ℝ
h : Subadditive u
L : ℝ
n : ℕ
hn : n ≠ 0
hL : u n / ↑n < L
r : ℕ
x✝ : r < n
A : Tendsto (fun x => (u n + u r / x) / (↑n + ↑r / x)) atTop (𝓝 ((u n + 0) / (↑n + 0)))
B : Tendsto (fun x => (x * u n + u r) / (x * ↑n + ↑r)) atTop (𝓝 (u n / ↑n))
k : ℕ
hk : ((fun x => (x * u n + u r) / (x * ↑n + ↑r)) ∘ Nat.cast) k < L
⊢ u (n * k + r) / ↑(n * k + r) < L
tactic: refine ((B.comp tendsto_natCast_atTop_atTop).eventually (gt_mem_nhds hL)).mono fun k hk => ?_
state_before: u : ℕ → ℝ
h : Subadditive u
L : ℝ
n : ℕ
hn : n ≠ 0
hL : u n / ↑n < L
r : ℕ
x✝ : r < n
A : Tendsto (fun x => (u n + u r / x) / (↑n + ↑r / x)) atTop (𝓝 ((u n + 0) / (↑n + 0)))
B : Tendsto (fun x => (x * u n + u r) / (x * ↑n + ↑r)) atTop (𝓝 (u n / ↑n))
k : ℕ
hk : ((fun x => (x * u n + u r) / (x * ↑n + ↑r)) ∘ Nat.cast) k < L
⊢ u (n * k + r) / ↑(n * k + r) < L
state_after: u : ℕ → ℝ
h : Subadditive u
L : ℝ
n : ℕ
hn : n ≠ 0
hL : u n / ↑n < L
r : ℕ
x✝ : r < n
A : Tendsto (fun x => (u n + u r / x) / (↑n + ↑r / x)) atTop (𝓝 ((u n + 0) / (↑n + 0)))
B : Tendsto (fun x => (x * u n + u r) / (x * ↑n + ↑r)) atTop (𝓝 (u n / ↑n))
k : ℕ
hk : ((fun x => (x * u n + u r) / (x * ↑n + ↑r)) ∘ Nat.cast) k < L
⊢ u (k * n + r) / ↑(k * n + r) < L
tactic: rw [mul_comm]
state_before: u : ℕ → ℝ
h : Subadditive u
L : ℝ
n : ℕ
hn : n ≠ 0
hL : u n / ↑n < L
r : ℕ
x✝ : r < n
A : Tendsto (fun x => (u n + u r / x) / (↑n + ↑r / x)) atTop (𝓝 ((u n + 0) / (↑n + 0)))
B : Tendsto (fun x => (x * u n + u r) / (x * ↑n + ↑r)) atTop (𝓝 (u n / ↑n))
k : ℕ
hk : ((fun x => (x * u n + u r) / (x * ↑n + ↑r)) ∘ Nat.cast) k < L
⊢ u (k * n + r) / ↑(k * n + r) < L
state_after: u : ℕ → ℝ
h : Subadditive u
L : ℝ
n : ℕ
hn : n ≠ 0
hL : u n / ↑n < L
r : ℕ
x✝ : r < n
A : Tendsto (fun x => (u n + u r / x) / (↑n + ↑r / x)) atTop (𝓝 ((u n + 0) / (↑n + 0)))
B : Tendsto (fun x => (x * u n + u r) / (x * ↑n + ↑r)) atTop (𝓝 (u n / ↑n))
k : ℕ
hk : ((fun x => (x * u n + u r) / (x * ↑n + ↑r)) ∘ Nat.cast) k < L
⊢ u (k * n + r) / ↑(k * n + r) ≤ ((fun x => (x * u n + u r) / (x * ↑n + ↑r)) ∘ Nat.cast) k
tactic: refine lt_of_le_of_lt ?_ hk
state_before: u : ℕ → ℝ
h : Subadditive u
L : ℝ
n : ℕ
hn : n ≠ 0
hL : u n / ↑n < L
r : ℕ
x✝ : r < n
A : Tendsto (fun x => (u n + u r / x) / (↑n + ↑r / x)) atTop (𝓝 ((u n + 0) / (↑n + 0)))
B : Tendsto (fun x => (x * u n + u r) / (x * ↑n + ↑r)) atTop (𝓝 (u n / ↑n))
k : ℕ
hk : ((fun x => (x * u n + u r) / (x * ↑n + ↑r)) ∘ Nat.cast) k < L
⊢ u (k * n + r) / ↑(k * n + r) ≤ (↑k * u n + u r) / ↑(k * n + r)
state_after: no goals
tactic: exact div_le_div_of_nonneg_right (h.apply_mul_add_le _ _ _) (Nat.cast_nonneg _)