Anybody know the right answer?

To find the displacement between t=0 and t=1, we want to plug 0 & 1 into the equations, then find the different in the answers.
When t = 0:
x = 4 cos(π(0)+π/4) → π · 0 = 0, so therefore:
x = 4 cos (π/4) → cos (π/4) = √2/2
x = 4 (√2/2)
x = 4√2/2 → 4 divided by 2 = 2, so we can simplify this to
x = 2√2
When t = 1:
x = 4 cos(π(1)+π/4) → π · 1 = π, so therefore:
x = 4 cos (π + π/4) → π + π/4 = 5π/4, so therefore
x = 4 cos (5π/4) → cosine of 5π/4 = -√2/2
x = 4 · -√2/2
x = -4√2/2 → -4 divided by 2 = -2, so we can simplify this to
x = -2√2
Answer: Then, we find the difference between x(0) and x(1), which is x(1)-x(0) =
-√2/2 - √2/2 = -√2