Question

Anybody know the right answer?

Answer 1

The displacement of interest is the value of x at t=1 minus the value of x at t=0.

At t=1

... x = 4cos(π+π/4) = 4·(-√2)/2 = -2√2

At t=0

... x = 4cos(π/4) = 4·(√2)/2 = 2√2

Then the difference (displacement) is

... -2√2 -(2√2) = -4√2 ≈ -5.6569