11. Using L.T. show that x + y + 2-c = x + 12. Show that cp - (j} + j} + j?) = cp . 13. Show that (E - cB) is relativistically invariant. -22-c4. 14. Show that (EB) is relativistically invariant. 15. Prove that (E - cB) is relativistically invariant. Hence show that if E = cB in one inertial frame, then E' = cB' in any other frame. 16. Prove that if the electric and magnetic fields are mutually perpendicular in one inertial frame, they must be mutually perpendicular in all inertial frames.