Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Dual cone and polar cone are closely related concepts in convex analysis, a branch of mathematics. Convex analysis is the branch of mathematics devoted to the study of properties of convex functions and convex sets, often with applications in convex optimization, a subdomain of optimization theory. In mathematics, Euclidean space is the Euclidean plane and three-dimensional space of Euclidean geometry, as well as the generalizations of these notions to higher dimensions. The term Euclidean is used to distinguish these spaces from the curved spaces of non-Euclidean geometry and Einstein''s general theory of relativity.