4. On Series Definitions of the Exponential, Cosine And Sine Functions

by Sunday Oluyemi  
Odo-Koto, Aiyedaade, Ilorin South LGA, Kwara State, NIGERIA.

Abstract
There are many methods, in the literature, of defining the exponential,
cosine and sine functions. One method is employing series to define them.
We here furnish a clear, simple and unflustered proof of convergence of
these series.

Keywords: Convergence Ratio Test, Alternating Series Test, the nth Term Test.