The motion of the particle P is the ellipse defined by the relations r = 2 / (2 - cos t) and =

The motion of the particle P is the ellipse defined by the relations r = 2 / (2 - cos π t) and θ = π t, where r is expressed in meters, θ in radians and t in seconds. Determine the velocity and acceleration of the particle when 

a) t = 0, 

b) t = 0.5 s.