Since t is from 0 to 1 second, the time length is 1 second total.
replace t in the given equation with 1 and solve for x:
x = 4 cos(PI x 1 + PI/4)
X = 4cos(PI + PI/4)
x = 4cos(5PI/4)
x = 4(-cos(PI/4))
x = -2√2
