Theorem 4.15.  Suppose  [Graphics:Images/ComplexPowerSeriesMod_gr_21.gif] .  Then the set of points z for which the series converges is one of the following:

(i)    The single point  [Graphics:Images/ComplexPowerSeriesMod_gr_22.gif].   

(ii)   The disk  [Graphics:Images/ComplexPowerSeriesMod_gr_23.gif],  along with part (either none, or some or all) of the circle  [Graphics:Images/ComplexPowerSeriesMod_gr_24.gif].  

(iii)  The entire complex plane.

Proof.

Proof of Theorem 4.15 is in the book.

Complex Analysis for Mathematics and Engineering