Frame S' has an x-component of velocity u relative to frame S, and at t = t' = 0 the two frames coincide (see Fig. 37.3). A light pulse with a spherical wave front is emitted at the origin of S' at time t' = 0. Its distance x' from the origin after a time t' is given by x’2 = c2t’2. Use the Lorentz coordinate transformation to transform this equation to an equation in x and t, and show that the result is x2 = c2t2; that is, the motion appears exactly the same in frame of reference S as it does in S'; the wave front is observed to be spherical in both frames.