1. The problem statement, all variables and given/known data Graph the magnitude and phase of the function: H(w) = cos(3w) 2. Relevant equations None 3. The attempt at a solution So here's the thing, I understand how to graph the phase and magnitude of any sort of function like X(w) = A*exp(wt). In that case, the magnitude would just be |X(w)| = A and the phase would be w. However, I'm not sure how to apply that to graphing a cosine. I know that it doesn't have any imaginary portions (I think), so the magnitude would be just the absolute value of the function, which would be the cos function with a period of (2*pi)/3 but with all the negative parts flipped over the x-axis. Using Matlab, I see that this is indeed the case: http://imageshack.us/a/img696/2913/magfc.jpg [Broken] However, I don't understand how to get the phase graph or why it is like it is: http://imageshack.us/a/img198/5306/phasen.jpg [Broken] Could someone explain this to me? Thanks in advance!