Theorem: IncidenceAlgebra.mu_apply (LeanCamCombi/Incidence.lean)

State before:
𝕄 : Type u_1
F : Type u_2
𝕜 : Type u_3
𝕝 : Type u_4
𝕞 : Type u_5
α : Type u_6
β : Type u_7
inst✝⁴ : AddCommGroup 𝕜
inst✝³ : One 𝕜
inst✝² : Preorder α
inst✝¹ : LocallyFiniteOrder α
inst✝ : DecidableEq α
a b : α
⊢ (mu 𝕜) a b = if a = b then 1 else -∑ x ∈ Ico a b, (mu 𝕜) a x
Tactic:
rw [mu, coe_mk, muAux_apply, sum_attach]
State after:
no goals