-- Mathlib/Analysis/Calculus/LineDeriv/Basic.lean
theorem Filter.EventuallyEq.lineDerivWithin_eq (hs : f₁ =ᶠ[𝓝[s] x] f) (hx : f₁ x = f x) :
    lineDerivWithin 𝕜 f₁ s x v = lineDerivWithin 𝕜 f s x v

Proof state:
𝕜 : Type u_1
inst✝⁴ : NontriviallyNormedField 𝕜
F : Type u_2
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace 𝕜 F
E : Type u_3
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace 𝕜 E
f f₁ : E → F
s : Set E
x v : E
hs : f₁ =ᶠ[𝓝[s] x] f
hx : f₁ x = f x
⊢ (fun t => f₁ (x + t • v)) =ᶠ[𝓝[(fun t => x + t • v) ⁻¹' s] 0] fun t => f (x + t • v)

Tactic:
have A : Continuous (fun (t : 𝕜) ↦ x + t • v) := by fun_prop

Result:
𝕜 : Type u_1
inst✝⁴ : NontriviallyNormedField 𝕜
F : Type u_2
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace 𝕜 F
E : Type u_3
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace 𝕜 E
f f₁ : E → F
s : Set E
x v : E
hs : f₁ =ᶠ[𝓝[s] x] f
hx : f₁ x = f x
A : Continuous fun t => x + t • v
⊢ (fun t => f₁ (x + t • v)) =ᶠ[𝓝[(fun t => x + t • v) ⁻¹' s] 0] fun t => f (x + t • v)

Proof state:
𝕜 : Type u_1
inst✝⁴ : NontriviallyNormedField 𝕜
F : Type u_2
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace 𝕜 F
E : Type u_3
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace 𝕜 E
f f₁ : E → F
s : Set E
x v : E
hs : f₁ =ᶠ[𝓝[s] x] f
hx : f₁ x = f x
⊢ lineDerivWithin 𝕜 f₁ s x v = lineDerivWithin 𝕜 f s x v

Tactic:
apply derivWithin_eq ?_ (by simpa using hx)

Result:
𝕜 : Type u_1
inst✝⁴ : NontriviallyNormedField 𝕜
F : Type u_2
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace 𝕜 F
E : Type u_3
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace 𝕜 E
f f₁ : E → F
s : Set E
x v : E
hs : f₁ =ᶠ[𝓝[s] x] f
hx : f₁ x = f x
⊢ (fun t => f₁ (x + t • v)) =ᶠ[𝓝[(fun t => x + t • v) ⁻¹' s] 0] fun t => f (x + t • v)

Proof state:
𝕜 : Type u_1
inst✝⁴ : NontriviallyNormedField 𝕜
F : Type u_2
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace 𝕜 F
E : Type u_3
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace 𝕜 E
f f₁ : E → F
s : Set E
x v : E
hs : f₁ =ᶠ[𝓝[s] x] f
hx : f₁ x = f x
A : Continuous fun t => x + t • v
⊢ x = x + 0 • v

Tactic:
simp

Result:
no goals

Proof state:
𝕜 : Type u_1
inst✝⁴ : NontriviallyNormedField 𝕜
F : Type u_2
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace 𝕜 F
E : Type u_3
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace 𝕜 E
f f₁ : E → F
s : Set E
x v : E
hs : f₁ =ᶠ[𝓝[s] x] f
hx : f₁ x = f x
A : Continuous fun t => x + t • v
⊢ (fun t => f₁ (x + t • v)) =ᶠ[𝓝[(fun t => x + t • v) ⁻¹' s] 0] fun t => f (x + t • v)

Tactic:
exact A.continuousWithinAt.preimage_mem_nhdsWithin'' hs (by simp)

Result:
no goals

Proof state:
𝕜 : Type u_1
inst✝⁴ : NontriviallyNormedField 𝕜
F : Type u_2
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace 𝕜 F
E : Type u_3
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace 𝕜 E
f f₁ : E → F
s : Set E
x v : E
hs : f₁ =ᶠ[𝓝[s] x] f
hx : f₁ x = f x
⊢ f₁ (x + 0 • v) = f (x + 0 • v)

Tactic:
simpa using hx

Result:
no goals

Proof state:
𝕜 : Type u_1
inst✝⁴ : NontriviallyNormedField 𝕜
F : Type u_2
inst✝³ : NormedAddCommGroup F
inst✝² : NormedSpace 𝕜 F
E : Type u_3
inst✝¹ : NormedAddCommGroup E
inst✝ : NormedSpace 𝕜 E
f f₁ : E → F
s : Set E
x v : E
hs : f₁ =ᶠ[𝓝[s] x] f
hx : f₁ x = f x
⊢ Continuous fun t => x + t • v

Tactic:
fun_prop

Result:
no goals