Use the special relativistic velocity addition law to show that if a particle has velocity v = tanh & then in a frame moving at velocity v = tanh along the same direction the velocity of the particle is given by dº = tanh(0 - 6) (b) a free particle is moving along the x-axis of an inertial frame with speed do = v, passing through the origin at time t = 0. express the particle's worldline parametri- cally in terms of v using the proper time as the parameter.