EXERCESE LES If the 4vectors U'I =2 y(u)(c, [1) (1.142) and V\" = y(v)(c, v) _ (1.143) are the 4-Vector velocities of two particles in some frame of reference, show that U\" Va = 1/04062 (1.144) where w is the relative velocity of the two particles as viewed in the rest frame of one particle or the other. Hint: Evaluate the expression rst in the rest frame of one particle, and then generalize