Paratingent cone


In mathematics, the paratingent cone and contingent cone were introduced by, and are closely related to tangent cones.

Definition

Let be a nonempty subset of a real normed space.
  1. Let some be given. An element is called a tangent to at, if there is a sequence of elements and a sequence of positive real numbers so that and
  2. The set of all tangents to at is called the contingent cone to at.