⑩天掌 Teaching Plan on Advanced Mathematics o △0z△u,0zAν,0(p) △tu△tav△t'M(p=y(△n)2+(△v)2) 令△t→0,则有△u→>0,△ν→0, △udu△pdy △tdt△tdt 0(P)_0(p) △2+( )0 A t pV△t (△t<0时,根式前加“-”号) dz a du az dy dt au dt ay dt (全导数公式) tianjin polytechnic dmivendityTianjin Polytechnic University Teaching Plan on Advanced Mathematics 则有u → 0, v → 0, ( 全导数公式 ) t v v z t u u z t z     +     =   t o  + (  ) z u v t t ( ( ) ( ) ) 2 2  = u + v ( )  o  = (△t＜0 时,根式前加“–”号) t v t v t u t u d d , d d →   →   t v v z t u u z t z d d d d d d     +   =