A power series (in one variable) is an infinite series. Any polynomial can be easily expressed as a power series around any center c, although most of the coefficients will be zero since a power series has infinitely many terms by definition. One can view power series as being like "polynomials of infinite degree," although power series are not polynomials. The content in this Textmap's chapter is complemented by OpenStax's Calculus Textmap.
Thumbnail: The graph shows the function \(\displaystyle y=sinx\) and the Maclaurin polynomials \(\displaystyle p_1,p_3\) and \(\displaystyle p_5\). Image used with permission (CC BY-SA 3.0; OpenStax).