f : ℕ → ℝ
hf : Tendsto f atTop atTop
r : ℝ
hf' : ∀ (b : ℝ), ∃ i, ∀ (a : ℕ), i ≤ a → b ≤ f a
i : ℕ
hi : ∀ (a : ℕ), i ≤ a → r + 1 ≤ f a
hi' : ∀ (a : ℕ), f a < r + 1 → a < i
⊢ {a | f a ≤ r} ⊆ {a | a ≤ i}
f : ℕ → ℝ
hf : Tendsto f atTop atTop
r : ℝ
hf' : ∀ (b : ℝ), ∃ i, ∀ (a : ℕ), i ≤ a → b ≤ f a
i : ℕ
hi : ∀ (a : ℕ), i ≤ a → r + 1 ≤ f a
hi' : ∀ (a : ℕ), f a < r + 1 → a < i
⊢ {a | r < f a}ᶜ ⊆ {a | a ≤ i}
simp only [Set.compl_setOf, not_lt]
no goals
f : ℕ → ℝ
hf : Tendsto f atTop atTop
r : ℝ
hf' : ∀ (b : ℝ), ∃ i, ∀ (a : ℕ), i ≤ a → b ≤ f a
i : ℕ
hi : ∀ (a : ℕ), i ≤ a → r + 1 ≤ f a
hi' : ∀ (a : ℕ), f a < r + 1 → a < i
⊢ {a | f a ≤ r} ⊆ {a | a ≤ i}
exact fun a har => le_of_lt (hi' a (lt_of_le_of_lt har (lt_add_one _)))