... le. Giaíi. () () () ( ) () () () yxetYetXtR;dttRdtVt,tRVrrrrrrr+=== Váûy () () ( ) x0yxebXedttdYedttdXtVrrrr=+= ( vç () 0dttdY= ) Hay () () ( ) xx0ebbt1tXebXt,tRVrrrr+== ... khi nọ âi qua l () tRr cọ phỉång trçnh sau: () () ()( ) () () ()( ) () () ()( ) dtt,tZ,tY,tXVdZt,tZ,tY,tXVdYt,tZ,tY,tXVdXZyx=== 2.Âỉåìng dng. ÅÍ thåìi âiãøm t0 â cho, âỉåìng dng ... () (tRr ) rr=. Vỏỷn tọỳc cuớa noù ồớ thồỡi gian t laỡ: () () () (t,tRVd ) ttRdtVrrrr== vaỡ ta coù: ( ) ( ) ( ) t,rvt,tRVrrrr= Vỏỷy vaỡ ()( t,rvt,Mvrrr= ) ( ) ( ) t,tRVrr...