(2)已知 =V(x,y,z)=dfrac ({x)^2}({a)^2}+dfrac ({y)^2}({b)^2}+dfrac ({z)^2}({c)^2}, 则 gradV=() .-|||-

殳 =(u)^2ln v =dfrac (y)(x), =2x-3y,-|||-则 dfrac (partial z)(partial y)= ()-|||-A

求椭球面dfrac ({x)^2}(2)+dfrac ({y)^2}(3)+dfrac ({z)^2}(4)=1上点dfrac ({x)^2}(2)+dfrac

直线dfrac (x-1)(2)=dfrac (y)(-1)=dfrac (z-2)(3)-|||-__与直线dfrac (x-1)(2)=dfrac (y)(

求下列函数的 dfrac ({a)^2z}(a{x)^2} ,dfrac ({partial )^2z}(partial xpartial y) ,dfrac

sin (x+2y-3z)=x+2y-3z, 则 dfrac (partial z)(partial x)+dfrac (partial z)(partial

下列选项中曲面dfrac ({x)^2}(4)+dfrac ({y)^2}(1)+dfrac ({z)^2}(9)=3上点dfrac ({x)^2}(4)+df

直线dfrac (x-1)(1)=dfrac (y)(2)=dfrac (z+3)(-2)-|||-__ __-|||-__与平面dfrac (x-1)(1)=

如果^2+(z)^2=ln dfrac (z)(x),则^2+(z)^2=ln dfrac (z)(x)( ).A.^2+(z)^2=ln dfrac (

1.已知 sin (3x-2y+z)=3x-2y+z, 则 dfrac ({partial )^2z}(partial xpartial y)= __

5.设 ,b,c,mu gt 0 ,曲面 =mu 与曲面 dfrac ({x)^2}({a)^2}+dfrac ({y)^2}({b)^2}+dfrac ({