Relativity, Physics, Math, Einstein, Spacetime.
this inexplicable equation is not required for derivation of the relativity relations; however, its utility is limited only to working out relations for Lorentz Transformation Condition. — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — By adding (or subtracting) equations