title: How to calculate the energy spectrum of a signal?
body: <p>I know by theory that the energy spectrum of a given signal is the <strong>sum of the squared fourier coefficient</strong>. </p>
  
  <p>What if I have the real and imaginary part of the corresponding fourier coefficient, can I say that energy spectrum of a given signal is equal to <strong>sum of (real part + imaginary part)^2</strong></p>