Aus Online Mathematik Brückenkurs 2

In words, the inequality says that the distance \displaystyle \left| z-i \right| between \displaystyle z and \displaystyle i should be strictly greater than \displaystyle \text{2} and less than or equal to \displaystyle \text{3}. This means that the inequality defines an annular set having an inner radius of \displaystyle \text{2} and outer radius of \displaystyle \text{3}, with centre at \displaystyle i.

The inner dashed is not included in the set; on the other hand, the outer solid circle does.