The equation r(t) = cos(2t) i + sin(2t) j, t20 describes the motion of a particle moving along the unit circle. Answer the following questions about the behavior of the particle. a. Does the particle have constant speed? If so, what is its constant speed? b. Is the particle's acceleration vector always orthogonal to its velocity vector? c. Does the particle move clockwise or counterclockwise around the circle? d. Does the particle begin at the point (1,0)? a. Select the correct choice below and fill in any answer boxes within your choice OA. The particle's constant speed is OB. The particle's speed is not constant.