[填空题]
Calculate the maximum kinetic energy oc4u4 m.:.ywpnu wjfvu 9: v:8ezro9zff the electron in rcezt arx/9ingm j0 xy10s;xq7/ v.*j+zt6wvthe decay $\mu^- \to e^- + \bar{\nu}_e + \nu_\mu$. [Hint: In what direction do the two neutrinos move relative to the electron in order to give the latter the maximum kinetic energy? Both energy and momentum are conserved; use relativistic formulas.] $\text{KE}_{\text{e}^-}$ MeV
