To recover the previous expressions for relative velocity, we assume that particle "A" is following the path defined by dx/dt in the unprimed reference (and hence "dx"′/"dt"′ in the primed frame). Thus formula_22 and formula_23, where formula_24 and formula_25 refer to motion of "A" as seen by an observer in the unprimed and primed frame, respectively. Recall that "v" is the motion of a stationary object in the primed frame, as seen from the unprimed frame. Thus we have formula_26, and: