Teach frequency response plots as three aligned panels from A(w)

Students who can factor H = e^(-jcw) A(w) often don't know what to do next. A three-panel stacked chart helps: A(w) with its negative regions shaded as scratch work, then |H| with those dips flipped up, then phase with jumps directly under each zero crossing. For hand work, a table at the w values where the cosine argument hits multiples of pi/2 is enough to sketch A. Add a separate zero solve when A has a constant term. Compare the plotted phase with the worked answer, since np.angle wraps it for you.