The problem is attached in the picture.
The Attempt at a Solution
This looks like a vector in polar notation to me (r, θ). But the application of vectors to phases and periodicity is not even mentioned in the chapter! (Vector Algebra)
I've tried to make sense of it but I'm not sure what's going on in the solutions..
What I think is this:
given 2 vectors of equal length, one with θ = 0 and another with θ = 45o, in a given amount of time the inclined vector travels a shorter distance along x. Specifically:
x' = x cos (45)
I'm not sure if i'm correct to analyse it in this way..