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Theorems · Theorem · group theory

Finset.sum_indicator_subset

∀ {ι : Type u_1} {β : Type u_4} [inst : AddCommMonoid β] (f : ι → β) {s t : Finset ι},
  s ⊆ t → ∑ i ∈ t, (↑s).indicator f i = ∑ i ∈ s, f i

Summing an indicator function over a possibly larger Finset is the same as summing the original function over the original finset.

Defined in
Mathlib.Algebra.BigOperators.Group.Finset.Indicator
Cited by
11 results in Mathlib
Foundations
Depth 69 from the axioms · uses propext, Classical.choice, Quot.sound
Assumes
AddCommMonoid

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