I am trying to expand an explicit piecewise equation as a Fourier series formulation using Wolfram Mathematica software.
An example of these expansions is depicted in this paper (Article Quantitative Analysis of Contribution of Airgap Field Harmon...
).The two piecewise multi-parameter equations (eq. 12 & 13) are transformed into two Fourier series equations (eq. 14 & 15).
What is the best way to go about performing this expansion and how?