theorem
proved
term proof
dAlembert_to_ODE_of_contDiff
show as:
view Lean formalization →
formal statement (Lean)
120theorem dAlembert_to_ODE_of_contDiff
121 (Hf : ℝ → ℝ)
122 (h_dAlembert : ∀ t u, Hf (t + u) + Hf (t - u) = 2 * Hf t * Hf u)
123 (h_diff : ContDiff ℝ 2 Hf)
124 (h_deriv2_zero : deriv (deriv Hf) 0 = 1) :
125 ∀ t, deriv (deriv Hf) t = Hf t := by
proof body
Term-mode proof.
126 intro t
127 have h_rel := dAlembert_second_deriv_at_zero_of_contDiff Hf h_dAlembert h_diff t
128 rw [h_deriv2_zero] at h_rel
129 linarith
130
131/-- Bridge from an explicit `ContDiff ℝ 2` hypothesis to the legacy ODE hypothesis. -/