Let $\Omega$ be a bounded domain (open connected) in the Euclidean space, that contains the origin. Is there a name/what can I call for the cone like region with tip at the origin and base at some portion of the boundary ?
It looks like what one sees when hold a flash light at the origin and there is a light spot on the "wall= a portion of the boundary ".
What if $\Omega$ is a ball, does that region have a particular name in this case? Thanks