English
A reiteration of the difference identity for mulIndicator, relating t \\ s to the quotients of the full and sub-indicators.
Русский
Повторение тождества разности индикаторов через частное от полного и частичных индикаторов.
LaTeX
$$$$ \\forall s \\subseteq t, \\forall f,\\ mulIndicator(t \\setminus s) f = mulIndicator t f / mulIndicator s f $$$$
Lean4
@[to_additive]
theorem map_mulIndicator {M N : Type*} [MulOneClass M] [MulOneClass N] (f : M →* N) (s : Set α) (g : α → M) (x : α) :
f (s.mulIndicator g x) = s.mulIndicator (f ∘ g) x := by simp [Set.mulIndicator_comp_of_one]