theorem extracted_formal_statement_1.{u_1} {E : Type u_1} {f : E → ℝ} {g : ℕ → E}
  (mono : ∀ (k : ℕ), f (g (k + 1)) ≤ f (g k)) : f (g 2) ≤ f (g 1) := sorry

State before:
case zero
E : Type u_1
f : E → ℝ
g : ℕ → E
mono : ∀ (k : ℕ), f (g (k + 1)) ≤ f (g k)
⊢ f (g 2) ≤ f (g 1)

Tactic: apply mono 1

State after:

Relevant lemmas: