1. The problem statement, all variables and given/known data Asked to calculate the relativistic correction, to the differential scattering cross section which is given by the equation below in terms of E, E0 and θ where E0= .511 MeV. with 100MeV electrons from an Au nuclei at certain angles θ. 2. Relevant equations Relativistic correction = [ 1 - (v0)2/c2.sin2(θ/2)] 3. The attempt at a solution I figure the electron energy is kinetic so 100MeV = 1/2 m v2 and by re-arranging for v i get; v = 200/E0 then plugging into the formular for v gives, (at 20°=θ) [1 - 200/E0c2.0.03 ] I'm not sure, first of all if this is correct do far and second of all how to express in terms of E, could it be to use; E = √(1-(v/c)2).mc2 and somehow re-arrange? Any help would be greatly appreciated. Cheers.