Periodic CT Signal
$ x(t) = cos(3\pi t+\pi) \! $ with fundamental frequency of $ \pi $
$ x(t) = \frac{e^{j(3\pi t+\pi)}+e^{-j(3\pi t+\pi)}}{2} $
$ = \frac{e^{j3\pi t}e^{\pi}+e^{-j3\pi t}e^{\pi}}{2} $
$ = \frac{-e^{j3\pi t}-e^{-j3\pi t}}{2} $
$ = -\frac{1}{2}e^{j3\pi t}-\frac{1}{2}e^{-j3\pi t} $
Fourier Series Coefficients
$ a_3 = -\frac{1}{2} $
$ a_{-3} = -\frac{1}{2} $
