rewrite [mul_comm_div]
case refine_2
α : Type u_1
ι : Type u_2
E : Type u_3
F : Type u_4
s : Set ι
inst✝² : TopologicalSpace ι
C : ι → E
c : F
inst✝¹ : NormedAddGroup E
inst✝ : SeminormedAddGroup F
hf : ContinuousOn C s
hs : IsCompact s
hC : ∀ i ∈ s, C i ≠ 0
l : Filter α
x : ι × α
hx : x ∈ s ×ˢ Set.univ
⊢ ‖c‖ ≤
    ‖c‖ / sInf (norm '' (C '' s)) *
      ‖match x with
        | (i, _x) => C i‖
case refine_2
α : Type u_1
ι : Type u_2
E : Type u_3
F : Type u_4
s : Set ι
inst✝² : TopologicalSpace ι
C : ι → E
c : F
inst✝¹ : NormedAddGroup E
inst✝ : SeminormedAddGroup F
hf : ContinuousOn C s
hs : IsCompact s
hC : ∀ i ∈ s, C i ≠ 0
l : Filter α
x : ι × α
hx : x ∈ s ×ˢ Set.univ
⊢ ‖c‖ ≤
    ‖c‖ *
      (‖match x with
          | (i, _x) => C i‖ /
        sInf (norm '' (C '' s)))