English
For measurable s,t, the a.e. equality under μ.restrict s of condExp μ generateFrom {s} equals the real part of μ restricted to s applied to t.
Русский
Для измеримых s,t a.e. равенство condExp μ generateFrom {s} по μ.restrict s даёт real-часть μ ограниченного до s, применённого к t.
LaTeX
$$$μ⟦t|generateFrom\\{s\\}\\wrighٹ⟧ =^a.e[μ.restrict s] μ\\,.real t$$$
Lean4
theorem condExp_set_generateFrom_singleton (hs : MeasurableSet s) (ht : MeasurableSet t) :
μ⟦t|generateFrom { s }⟧ =ᵐ[μ.restrict s] fun _ ↦ μ[|s].real t :=
by
rw [← integral_indicator_one ht]
exact condExp_generateFrom_singleton hs <| Integrable.indicator (integrable_const 1) ht