English
For deterministic f: X → Y, the kernel composition with copy equals copy composed with deterministic: deterministic f ∥ copy equals copy composed with deterministic f.
Русский
Для детерминированной отображения копирование и композиция ядра commute.
LaTeX
$$$$ (\\text{deterministic } f) \\parallel\\! (\\text{copy } f) = (\\text{copy } f) \\circ (\\text{deterministic } f) $$$$
Lean4
theorem setIntegral_comp {f : γ → E} {s : Set γ} (hs : MeasurableSet s) (hf : IntegrableOn f s ((η ∘ₖ κ) a)) :
∫ z in s, f z ∂(η ∘ₖ κ) a = ∫ x, ∫ y in s, f y ∂η x ∂κ a :=
by
rw [← restrict_apply (η ∘ₖ κ) hs, ← comp_restrict hs, integral_comp]
· simp_rw [restrict_apply]
· rwa [comp_restrict, restrict_apply]