An electron e with kinetic energy 1.000 mev makes a head-on collision with a positron e at rest. (a positron is an antimatter particle that has the same mass as the electron but opposite charge.) in the collision the two particles annihilate each other and are replaced by two photons of equal energy, each traveling at angles θ with the electron's direction of motion. the reaction is show that the angle is cos θ--il a) c lity