rw [convexIndependent_set_iff_not_mem_convexHull_diff] at hs
case refine'_2
𝕜 : Type u_1
E : Type u_2
inst✝² : LinearOrderedField 𝕜
inst✝¹ : AddCommGroup E
inst✝ : Module 𝕜 E
s t : Set E
x : E
hs : ConvexIndependent 𝕜 fun p => ↑p
⊢ extremePoints 𝕜 ((convexHull 𝕜) s) = s
case refine'_2
𝕜 : Type u_1
E : Type u_2
inst✝² : LinearOrderedField 𝕜
inst✝¹ : AddCommGroup E
inst✝ : Module 𝕜 E
s t : Set E
x : E
hs : ∀ x ∈ s, x ∉ (convexHull 𝕜) (s \ {x})
⊢ extremePoints 𝕜 ((convexHull 𝕜) s) = s