Module: Mathlib.MeasureTheory.Measure.Lebesgue.VolumeOfBalls

Goal state before:
pp: case e'_2
E : Type u_1
inst✝⁸ : AddCommGroup E
inst✝⁷ : Module ℝ E
inst✝⁶ : FiniteDimensional ℝ E
mE : MeasurableSpace E
tE : TopologicalSpace E
inst✝⁵ : IsTopologicalAddGroup E
inst✝⁴ : BorelSpace E
inst✝³ : T2Space E
inst✝² : ContinuousSMul ℝ E
μ : Measure E
inst✝¹ : μ.IsAddHaarMeasure
g : E → ℝ
h1 : g 0 = 0
h2 : ∀ (x : E), g (-x) = g x
h3 : ∀ (x y : E), g (x + y) ≤ g x + g y
h4 : ∀ {x : E}, g x = 0 → x = 0
h5 : ∀ (r : ℝ) (x : E), g (r • x) ≤ |r| * g x
inst✝ : Nontrivial E
r : ℝ
F : Type u_1 := E
p : AddGroupNorm F := { toFun := g, map_zero' := h1, add_le' := h3, neg' := h2, eq_zero_of_map_eq_zero' := ⋯ }
this✝³ : NormedAddCommGroup F := p.toNormedAddCommGroup
this✝² : NormedSpace ℝ F := { toModule := inst✝⁷, norm_smul_le := ⋯ }
this✝¹ : TopologicalSpace F := PseudoMetricSpace.toUniformSpace.toTopologicalSpace
this✝ : MeasurableSpace F := borel F
this : BorelSpace F
φ : E ≃L[ℝ] F := (LinearEquiv.refl ℝ E).toContinuousLinearEquiv
ν : Measure F := map (⇑φ) μ
⊢ μ {x | g x ≤ r} = ν (Metric.closedBall 0 r)

pp: case e'_3
E : Type u_1
inst✝⁸ : AddCommGroup E
inst✝⁷ : Module ℝ E
inst✝⁶ : FiniteDimensional ℝ E
mE : MeasurableSpace E
tE : TopologicalSpace E
inst✝⁵ : IsTopologicalAddGroup E
inst✝⁴ : BorelSpace E
inst✝³ : T2Space E
inst✝² : ContinuousSMul ℝ E
μ : Measure E
inst✝¹ : μ.IsAddHaarMeasure
g : E → ℝ
h1 : g 0 = 0
h2 : ∀ (x : E), g (-x) = g x
h3 : ∀ (x y : E), g (x + y) ≤ g x + g y
h4 : ∀ {x : E}, g x = 0 → x = 0
h5 : ∀ (r : ℝ) (x : E), g (r • x) ≤ |r| * g x
inst✝ : Nontrivial E
r : ℝ
F : Type u_1 := E
p : AddGroupNorm F := { toFun := g, map_zero' := h1, add_le' := h3, neg' := h2, eq_zero_of_map_eq_zero' := ⋯ }
this✝³ : NormedAddCommGroup F := p.toNormedAddCommGroup
this✝² : NormedSpace ℝ F := { toModule := inst✝⁷, norm_smul_le := ⋯ }
this✝¹ : TopologicalSpace F := PseudoMetricSpace.toUniformSpace.toTopologicalSpace
this✝ : MeasurableSpace F := borel F
this : BorelSpace F
φ : E ≃L[ℝ] F := (LinearEquiv.refl ℝ E).toContinuousLinearEquiv
ν : Measure F := map (⇑φ) μ
⊢ μ {x | g x < r} = ν (Metric.ball 0 r)

Tactic:
· rw [@Measure.map_apply E F mE _ μ φ _ _ measurableSet_closedBall]
    · congr!
      simp_rw [Metric.closedBall, dist_zero_right]
      rfl
    · refine @Continuous.measurable E F tE mE _ _ _ _ φ ?_
      exact @ContinuousLinearEquiv.continuous ℝ ℝ _ _ _ _ _ _ E tE _ F _ _ _ _ φ

Goal state after:
case e'_3
E : Type u_1
inst✝⁸ : AddCommGroup E
inst✝⁷ : Module ℝ E
inst✝⁶ : FiniteDimensional ℝ E
mE : MeasurableSpace E
tE : TopologicalSpace E
inst✝⁵ : IsTopologicalAddGroup E
inst✝⁴ : BorelSpace E
inst✝³ : T2Space E
inst✝² : ContinuousSMul ℝ E
μ : Measure E
inst✝¹ : μ.IsAddHaarMeasure
g : E → ℝ
h1 : g 0 = 0
h2 : ∀ (x : E), g (-x) = g x
h3 : ∀ (x y : E), g (x + y) ≤ g x + g y
h4 : ∀ {x : E}, g x = 0 → x = 0
h5 : ∀ (r : ℝ) (x : E), g (r • x) ≤ |r| * g x
inst✝ : Nontrivial E
r : ℝ
F : Type u_1 := E
p : AddGroupNorm F := { toFun := g, map_zero' := h1, add_le' := h3, neg' := h2, eq_zero_of_map_eq_zero' := ⋯ }
this✝³ : NormedAddCommGroup F := p.toNormedAddCommGroup
this✝² : NormedSpace ℝ F := { toModule := inst✝⁷, norm_smul_le := ⋯ }
this✝¹ : TopologicalSpace F := PseudoMetricSpace.toUniformSpace.toTopologicalSpace
this✝ : MeasurableSpace F := borel F
this : BorelSpace F
φ : E ≃L[ℝ] F := (LinearEquiv.refl ℝ E).toContinuousLinearEquiv
ν : Measure F := map (⇑φ) μ
⊢ μ {x | g x < r} = ν (Metric.ball 0 r)