t,
t
as t varies in the interval 
Solution: When t = 1 , x = -1 and y = 0. When t = 1.5, x = 0 and y = -1 and finally at t = 2, x = 1 and y = 0. Therefore, the particle is traveling in the counterclockwise direction around a semicircle starting at the point (-1,0) and ending at (1,0):
As for the cartesian equation, since x = cos(Pi t) and y = sin(Pi t) it follows that
That is, the particle travels around the circle
from (-1,0) to (1,0).
by:sh