Dual curve: Difference between revisions

Similarly, generalizing to higher dimensions, given a [[hypersurface]], the [[tangent space]] at each point gives a family of [[hyperplane]]s, and thus defines a dual hypersurface in the dual space. For any closed subvariety {{mvar|X}} in a projective space, the set of all hyperplanes tangent to some point of {{mvar|X}} is a closed subvariety of the dual of the projective projectivespace, called the '''dual variety''' of {{mvar|X}}.