r(e)cos ly=r(O) 8 ∫Pd+Q小 d 从a→月a FPac+g小+Rh P y=y z=o(t) (PIo(),(t),a(t)lo'(t t从a→B + elo(t),y(t), a(tly'(t rIo(t),(t),a(tla(tft K心 . ( )sin ( )cos           Pdx Qdy d y r x r L  = = → + ========  从 R t t t t dt Q t t t t P t t t t Pdx Qdy Rdz z t y t x t t [ ( ), ( ), ( )] ( )} [ ( ), ( ), ( )] ( ) { [ ( ), ( ), ( )] ( ) ( ) ( ) ( )                    +  +  =====  + +       = = = →  从