Exercise 16.  Prove that    is the set of accumulation points of  

16 (a).  The set  .   

Solution 16 (a).

See text and/or instructor's solution manual.

    Since    is an open set, every point of    is an accumulation point of  .  

The boundary of    is the unit circle and  each point of   is also an accumulation point of  .  

No point of the exterior    is an accumulation point of  .

Therefore the set of accumulation points of is  .

This solution is complements of the authors.

(c) 2008 John H. Mathews, Russell W. Howell