A particle P moves with a constant speed v around the circular path of radius r. Start with the expression r=rr1 for the position vector of P and derive the expressions for the velocity v and acceleration a of P. The radial and transvers unit vectors are r1 and theta1 respectively.

so I know that with cartesian coordinates the position equation would be

rcos(theta)**i**+rsin(theta)**j **but after that I'm a little bit stuck. The teacher made some comment about recognizing that theta is dependent on time.