Here is a YouTube video about Basics of the Fourier Series, and is part of a growing collection of videos I have found to be useful. The reason is introducing the Fourier series and how to calculate them and understanding science related to software defined radio.
This tutorial, "Basics of the Fourier Series" is free education you can watch, which will help you deepen your knowledge and be better prepared for licence exams, schoolwork, or operating radio equipment.