Chapter 11.3, Problem 69E

Any method

1. a. Use any analytical method to find the first four nonzero terms of the Taylor series centered at 0 for the following functions. You do not need to use the definition of the Taylor series coefficients.
2. b. Determine the radius of convergence of the series.

63. $f(x)=\frac{e^x+e^{-x}}{2}$