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4 changes: 2 additions & 2 deletions Mathlib/MeasureTheory/Integral/Lebesgue/Map.lean
Original file line number Diff line number Diff line change
Expand Up @@ -72,8 +72,8 @@ theorem setLIntegral_map {f : β → ℝ≥0∞} {g : α → β} {s : Set β}
theorem lintegral_indicator_const_comp {f : α → β} {s : Set β}
(hf : Measurable f) (hs : MeasurableSet s) (c : ℝ≥0∞) :
∫⁻ a, s.indicator (fun _ => c) (f a) ∂μ = c * μ (f ⁻¹' s) := by
erw [lintegral_comp (measurable_const.indicator hs) hf]
rw [lintegral_indicator_const hs, Measure.map_apply hf hs]
rw [← lintegral_map (measurable_const.indicator hs) hf, lintegral_indicator_const hs,
Measure.map_apply hf hs]

/-- If `g : α → β` is a measurable embedding and `f : β → ℝ≥0∞` is any function (not necessarily
measurable), then `∫⁻ a, f a ∂(map g μ) = ∫⁻ a, f (g a) ∂μ`. Compare with `lintegral_map` which
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