x=o(t) (3推广r:{y=v(O,施点a终点 (t) Pdx + ody+ rdz =P|(),v(t),o()l() +olo(o,(,a(tly(t) + ro(t),y(),@(t)la(todt 上一页下一页返回, , . ( ) ( ) ( ) (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 [ ( ), ( ), ( )] ( )} [ ( ), ( ), ( )] ( ) { [ ( ), ( ), ( )] ( )               +  +  =  + +  