Theorem: Tutorial.IsLocalExtr.hasDerivAt_eq_zero (Tutorial/Advanced/Analysis/Lecture2.lean)

State before:
f : ℝ → ℝ
f' x a b : ℝ
h : IsLocalExtr f a
hf : HasDerivAt f f' a
⊢ f' = 0
Tactic:
sorry
State after:
no goals