Guess The Signal
1. The signal is periodic with a period of 3 seconds
2. The signal is modeled by an odd and real function
3. The energy of the signal over one revolution (0 to $ 2\pi $) is $ 81 \pi $
4. The Fourier coefficients of the signal are 0 for all $ a_{k} $ except $ a_{1} $ and $ a_{-1} $
Answer
$ \ x(t) = 9 \sin(\frac{2 \pi}{3}t) $
