This video provides solved problems on the exponential Fourier series.
Fourier series representation
https://youtu.be/ockJIlUSv_Y
Trigonometric Fourier Series ( PART-1)
https://youtu.be/6PXG14-Vwws
Trigonometric Fourier Series ( PART-2)
https://youtu.be/o-Z_zJ9MT7A
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