no goals
E : Type u_1
inst✝ : SeminormedCommGroup E
ε δ : ℝ
s t : Set E
x y : E
hs : IsCompact s
hδ : 0 ≤ δ
⊢ closedBall 1 δ / s = cthickening δ s⁻¹
simp [div_eq_mul_inv, mul_comm, hs.inv.mul_closedBall_one hδ]