∀ {V : Type u_1} [inst : NormedAddCommGroup V] [inst_1 : InnerProductSpace ℝ V] {P : Type u_2} [inst_2 : MetricSpace P]
  [inst_3 : NormedAddTorsor V P] {s : EuclideanGeometry.Sphere P} {t p : P},
  s.IsTangentAt t (affineSpan ℝ {p, t}) → s.power p = dist p t ^ 2