Theorem: ENat.tsum_biUnion_le_tsum (Matroid/ForMathlib/ENatTopology.lean)

State before:
α : Type u_1
β : Type u_2
ι : Type u_3
s✝ : Set α
n : ℕ∞
f✝ g f : α → ℕ∞
s : Set ι
t : ι → Set α
⊢ ∑' (x : ↑(⋃ i ∈ s, t i)), f ↑x = ∑' (x : ↑(⋃ i, t ↑i)), f ↑x
Tactic:
rw [tsum_congr_subtype]
State after:
case h
α : Type u_1
β : Type u_2
ι : Type u_3
s✝ : Set α
n : ℕ∞
f✝ g f : α → ℕ∞
s : Set ι
t : ι → Set α
⊢ ∀ (x : α), x ∈ ⋃ i ∈ s, t i ↔ x ∈ ⋃ i, t ↑i

State before:
case h
α : Type u_1
β : Type u_2
ι : Type u_3
s✝ : Set α
n : ℕ∞
f✝ g f : α → ℕ∞
s : Set ι
t : ι → Set α
⊢ ∀ (x : α), x ∈ ⋃ i ∈ s, t i ↔ x ∈ ⋃ i, t ↑i
Tactic:
simp
State after:
no goals