(a) A stationary particle 1 decays into particles 2 and 3, which move off with equal but oppositely directed momenta. Show that the kinetic energy K2 of particle 2 is given by where K2 = 1/2E1 [(E1 – E2)2 – E23}, where E1, E2, and E3 are the rest energies of the particles.

(b) Show that the result in (a) yields the kinetic energy of the muon as calculated in Sample Problem