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lemma proved term proof

deriv_add_lin

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formal statement (Lean)

  60lemma deriv_add_lin (f g : (Fin 4 → ℝ) → ℝ) (μ : Fin 4)
  61    (x : Fin 4 → ℝ) (hf : DifferentiableAt ℝ (fun t => f (coordRay x μ t)) 0)
  62    (hg : DifferentiableAt ℝ (fun t => g (coordRay x μ t)) 0) :
  63  partialDeriv_v2 (fun y => f y + g y) μ x =
  64    partialDeriv_v2 f μ x + partialDeriv_v2 g μ x := by

proof body

Term-mode proof.

  65  unfold partialDeriv_v2
  66  exact deriv_add hf hg
  67
  68/-- Linearity of directional derivative (scalar multiplication). -/

depends on (9)

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