Propertise of a Dual Cone

Question

In Convex Optimization by Boyd (P.51) said that " $y\in K^*$ iff $-y$ is the normal of hyperplane that supports $k$ at the origin ($K^*$ is a dual cone of $K$) " what does it mean geometrically? I mean could someone please show me a figure that shows a dual cone of a cone

Answer 1

Wikipedia has some nice images:

http://en.wikipedia.org/wiki/Dual_cone_and_polar_cone

Does this help?