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