∀ {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] {a b t p : P} {s : EuclideanGeometry.Sphere P},
  a ∈ s → b ∈ s → p ∈ affineSpan ℝ {a, b} → s.IsTangentAt t (affineSpan ℝ {p, t}) → dist p t ^ 2 = dist p a * dist p b