That is a super helpful way to visualise it. I forgot WA can create these 3D Plots. Hell, I forgot 3D visualisations are a thing at all. Thanks for that!

Ah, and [-2, 2] is the range of possible values for the sum because [-1, 1] are the possible values of sin (and cos)?

How do you figure out the right-hand sides (0, 0.2, 1, 1.9)? Just guess random numbers and see what happens, or is there some heuristic for starting the guess?