Osculating Sphere
osculating sphere
[¦äs·kyə‚lād·iŋ ′sfir]Osculating Sphere
The osculating sphere of a space curve l at a point M is the sphere having contact of order n ≥ 3 with l at M. The osculating sphere can also be defined as the limit of a variable sphere passing through four points of l as the points tend to M.
The radius of the osculating sphere is
where ρ is the radius of curvature of l at M, ̓ is the torsion of l, and ds is the differential of arc of l.