lemma
proved
tactic proof
G_even_of_reciprocal_symmetry
show as:
view Lean formalization →
formal statement (Lean)
42lemma G_even_of_reciprocal_symmetry
43 (F : ℝ → ℝ)
44 (hSymm : ∀ {x : ℝ}, 0 < x → F x = F x⁻¹) :
45 Function.Even (G F) := by
proof body
Tactic-mode proof.
46 intro t
47 have hpos : 0 < Real.exp t := Real.exp_pos t
48 have hrec : Real.exp (-t) = (Real.exp t)⁻¹ := by simp [Real.exp_neg]
49 simp [G, hrec, hSymm hpos]
50