Theorem 5.1 (The exponential function).  The function    is an entire function satisfying the following conditions:

(iii).   If    is a real number, then   .  

Demonstration for Theorem 5.1 (iii).

This is DeMoivre's formula that was studied in Section 1.5.

(c) 2006 John H. Mathews, Russell W. Howell