W is the region outside of a sphere with r=5
what is the boundary ?
sorry this might be a silly question. i'm just debating between nothing or the sphere
It would be useful to remember that (at least in $\displaystyle \mathbb{R}^n$) $\displaystyle \partial \Omega = \overline{ \Omega } \cap \overline{ \mathbb{R} ^n \setminus \Omega }$ ie. the boundary of a set is the same as that of it's complement.