P-3.13 The signal x(t) in Fig. P-3.13 consists of a DC component plus a cosine signal. x(t) 20 10 0 N V -10 -20 -10 0 10 20 30 40 Timet (ms) Figure P-3.13 (a) Determine the frequency of the DC component, as well as the frequency of the cosine component. (b) Write an equation for the signal x(t). You should be able to determine numerical values for all the amplitudes, frequencies, and phases in your equation by inspection of the above graph. (c) Expand the equation obtained in the previous part into a sum of complex exponential signals with positive and negative frequency components. (d) Plot the two-sided spectrum of the signal x(t). Label the complex amplitudes for each positive and negative frequency component in the spectrum.