Question: 1. Find a trigonometric Fourier series representation of the function s(t) = cos π t in the interval 0 < t=""><>
2. Which of the following could not be the Fourier series expansion of a periodic signal?
s1(t) = 2cos t + 3cos 3t
s2(t) = 2cos 0.5t + 3cos 3.5t
s3(t) = 2cos 0.25t + 3cos 0.00054t
s4(t) = 2cos Πt + 3cos 2t
s4(t) = 2cos Πt + 3cos 2Πt