x=o(t) 上(3)推广r:1{y=v(,:点a,终点月 (t) Pdx +ody+rdz =mPg(,y(,o0)g() +Q|(t),y(t),o()y'(t) +ro(t),(),o(to(t)jdt 上页, , . ( ) ( ) ( ) (3) :      推广 t起点 终点 z t y t x t      = = =  R t t t t dt Q t t t t P t t t t Pdx Qdy Rdz [ ( ), ( ), ( )] ( )} [ ( ), ( ), ( )] ( ) { [ ( ), ( ), ( )] ( )               +  +  =  + +  