theorem extracted_formal_statement_8 (g : { t // t > 0 } → ℝ) (t_min : { t // t > 0 })
  (h_exp : ∀ (t : { t // t > 0 }), rexp (g t) ≥ rexp (g t_min)) : rexp (g t_min) ≤ ⨅ t, rexp (g t) := sorry

State before:
case a
ε a b : ℝ
m : ℕ
hm : m > 0
hε : ε > 0
hab : b > a
g✝ : { t // t > 0 } → ℝ := fun t => -↑t * ε + ↑t ^ 2 * ↑m * (b - a) ^ 2 / 8
t_min✝ : { t // t > 0 } := ⟨4 * ε / ((b - a) ^ 2 * ↑m), ⋯⟩
gt : ∀ (t : { t // t > 0 }), g✝ t = -↑t * ε + ↑t ^ 2 * ↑m * (b - a) ^ 2 / 8
h_rewrite : ∀ (t : { t // t > 0 }), g✝ t = ↑m * (b - a) ^ 2 / 8 * (↑t - ↑t_min✝) ^ 2 - 2 * ε ^ 2 / ((b - a) ^ 2 * ↑m)
h_inf : ∀ (t : { t // t > 0 }), g✝ t ≥ g✝ t_min✝
h_exp✝ : ∀ (t : { t // t > 0 }), rexp (g✝ t) ≥ rexp (g✝ t_min✝)
h_g_tmin : g✝ t_min✝ = -2 * ε ^ 2 / ((b - a) ^ 2 * ↑m)
h_exp_tmin : rexp (g✝ t_min✝) = rexp (-2 * ε ^ 2 / ((b - a) ^ 2 * ↑m))
h_inf_rewrite : ⨅ t, rexp (-↑t * ε + ↑t ^ 2 * ↑m * (b - a) ^ 2 / 8) = ⨅ t, rexp (g✝ t)
g : { t // t > 0 } → ℝ
t_min : { t // t > 0 }
h_exp : ∀ (t : { t // t > 0 }), rexp (g t) ≥ rexp (g t_min)
positive_reals_nonempty : Nonempty { t // t > 0 }
⊢ rexp (g t_min) ≤ ⨅ t, rexp (g t)

Tactic: apply le_ciInf
    intro t
    exact (h_exp t)

State after:

Relevant lemmas:
le_ciInf : ∀ {α : Type u_1} {ι : Sort u_4} [inst : ConditionallyCompleteLattice α] [inst_1 : Nonempty ι] {f : ι → α}
  {c : α}, (∀ (x : ι), c ≤ f x) → c ≤ iInf f