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[Merged by Bors] - feat: Add congr_deriv lemmas mirroring congr_fderiv #9065

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11 changes: 11 additions & 0 deletions Mathlib/Analysis/Calculus/Deriv/Basic.lean
Original file line number Diff line number Diff line change
Expand Up @@ -614,6 +614,17 @@ theorem Filter.EventuallyEq.hasDerivWithinAt_iff_of_mem (h₁ : f₁ =ᶠ[𝓝[s
⟨fun h' ↦ h'.congr_of_eventuallyEq_of_mem h₁.symm hx,
fun h' ↦ h'.congr_of_eventuallyEq_of_mem h₁ hx⟩

theorem HasStrictDerivAt.congr_deriv (h : HasStrictDerivAt f f' x) (h' : f' = g') :
HasStrictDerivAt f g' x :=
h.congr_fderiv <| congr_arg _ h'

theorem HasDerivAt.congr_deriv (h : HasDerivAt f f' x) (h' : f' = g') : HasDerivAt f g' x :=
HasFDerivAt.congr_fderiv h <| congr_arg _ h'

theorem HasDerivWithinAt.congr_deriv (h : HasDerivWithinAt f f' s x) (h' : f' = g') :
HasDerivWithinAt f g' s x :=
HasFDerivWithinAt.congr_fderiv h <| congr_arg _ h'

theorem HasDerivAt.congr_of_eventuallyEq (h : HasDerivAt f f' x) (h₁ : f₁ =ᶠ[𝓝 x] f) :
HasDerivAt f₁ f' x :=
HasDerivAtFilter.congr_of_eventuallyEq h h₁ (mem_of_mem_nhds h₁ : _)
Expand Down